Overall an incredibly good balanced solo game resulted, where my own preferences were taken out of the equation.
Solo rule tweaks
1. Posture (option selection): assuming there to be element options, each side dices as usual for aggressor/defender, but also opts for 'posture' based on odd or even result of the d6:
1,3,5=options favour defence
2,4,6=options favour attack
Defensive: this side's options are the ones that rely more on the enemy advancing. For example if a choice includes artillery, artillery is chosen.
Attacking: this side's options are the ones most likely to take the fight to the enemy. For example if a choice of foot or mounted, mounted is chosen.
Note that a 2nd dice should be rolled at the same time to decide deployment (3 below), or aggressor dice score needs to be noted down now.
Option 1, 3d6 per quarter.
Divide the board into quarters as per rulebook, but just roll 3 distinct dice for each.
1st dice is the x axis
2nd dice is the y axis
3rd dice is size (or possibly height - needs a bit of teaking - for example a 1 would be no height, a 6 might be at least 2 edges are impassable)
And if x=y, the piece either runs across the quadrant or sits on an edge, depending on value.
This option then proceeds to side selection as per rulebook.
Option 2, select/de-select.
The defender lays out terrain as usual, the aggressor may de-select two items or select one. An element that corsses two quadrants counts as two items. A BUA may not be de-selected, but may be altered to be walled or unwalled as a selection choice.
This option cancels the rulebook side selection: the defender simply chooses and sets camp.
3. Deployment:This relates back to posture in (1) above. Allowing for terrain restrictions, each side's deployment is governed by a second dice roll, added to the aggressor d6:
11,12: Left-weighted. At least four elements are included fully within the left third of deployment zone
9-10: Right-weighted. At least four elements or three including command are included fully within the right third of deployment zone
5-8: Centre-weighted. Command and at least four other elements are included fully within the centre third of deployment zone
2-4: Reserved. A defensive posture army includes at least three elements as a reserve; an attacking posture army must leave a strong defender element in its camp.
4. Axis: Each round an extra distinct dice is rolled:
1-3: Continue on existing axis of attack.
4,5: Shift axis of attack left. If already left, axis rotates around to right.
6: Shift axis of attack right. If already right, axis rotates around to left.
Set-up phase 1, defender/postureLater Carthaginian II32a Ag4+[rnd3]=7; defensive posture
Polybian Roman II33 Ag3=[rnd4]=7; attacking posture
In the event the posture is more useful than the normal aggressor dicing. The two opponents score the same total, but Polybian Romans (PRom) [rnd4] score attacking posture and Later Carthaginians (LCart) [rnd3] score defensive.
No need to reroll.
This is how the two sides are composed given the posture of each:
CvGen, Cv, 2xLH (1xIberian, 1xNumidian) 3xLibyan 4Sp, 1xLigurian 4Ax, 2xIberian 4Ax, 2xPs (1x javelin, 1x sling).
CvGen (tribune), Cv (equites), 4x4Bd (2xhastati, 2xprincipes) 2x4Sp (triarii) 2x4Ax (bruttii) 2xPs (velites) 1xCF.
Set-up phase 2, terrain and sideI use the 3d6 option. I'm not sure I got this right and make a note to tweak this next time. What I can say is that randomness took the danger of favouring one side over the other, out of the equation.
PRom nominate, and get, the 'cluttered' end of the board, woods on right, low hill near centre, low hill left flank.
Set-up phase 3, deploymentLCart as defender begins. They have a  from the posture dice and roll a further  for a total of 9. That means right-weighted deployment. Camp is set down on the right third.
PRom have a  from posture and roll  again for a total of 8, which means centre-weighted. Camp is set down at centre.
I find this takes the 'heat' out of solo deployment, where it is all too easy to second-guess and give one side a big advantage. To make it even easier, when I set up PRom second, I do a form of blind set-up so as not to look too closely at the LCart.
Deployment notes:LCart: 1xLibyan Sp is placed in camp. Posture does not mandate this but they are defensive and there is no friendly terrain to block an advance on the camp. LH are on the right, outside of Ps Cv and command. So 7 elements including command and camp are in the right third. In hindsight there is no need to crowd LH forward to the 'start line'. I'm not a naturally defensive player.
LCart PIP6, axis 6=switch right (axis rotates round to left)LH wheel and race across to the left flank! Main body wheels left, Ps spead out to at least mark the right flank.
PRom PIP6, axis 1=stick to planUnconcerned, tribune sends velites flying to the woods, hastati extend onto low hill, principes advance in column, and the Brutti head left to dominate the Ps.
LCart PIP1, axis 6=switch rightLH are left as is, instead Iberian Cv are detached to counter Ax. Here I confess to fluffing the Cv move and short-changing them, but I did it consistently throughout the game. A simple wheel of the main body would have achieved much the same, had I realised that Cv can race 4BW.
PRom PIP5, axis 4=switch leftTribune sends his equites to bolster the Brutti and extends principes and Brutti to form a strong line.
LCart PIP1, axis 4=switch leftIt's time to get the centre moving! The wheel that probably should have been made last bound occurs.
PRom PIP2, axis 4=switch left (rotates to right)Tribune uses those velites to ZOC the LCart LH. Distance is beginning to hurt.
LCart PIP4, axis 5=switch leftGeneral feeds elements left to counter the velites and with the extra PIPs pulls the LH out.
PRom PIP1, axis 2=remain rightThe rearmost velites filters into the woods to ZOC the Ligurian Ax! The woods-bound velites is now out of command range.
LCart PIP1 axis 1=remain leftPs are too tempting a target! Melee: even (I messed up - Ps should recoil from solid Ax). Ligurians are also out of range.
PRom PIP4, axis 6=switch right (rotates round to left)Principes and Brutti advance and equites sweep round to menace the hapless Ps. Reserves (triarii and tribune) advance, gaining enough command range to send uncommitted velites in.
Melee: Ligurian Ax lose by 2, not doubled, recoil
LCart PIP6, axis 3=remain leftPips are spent left to begin with, Iberian Ax reinforcing the Ligurians, and LH flank-lap velites to menace the PRom right. Spare PIPs can now be spent: LibySp double up, releasing reserve Iberian Ax.
Melee 1: Ax +3 v Ps +2-1 lapped: Ps doubled and destroyed.
Melee 2: Ax +3 v Ps +2-1 lapped: Ps not doubled, recoils.
PRom PIP2, axis 6=switch right (to centre)Hastati advance down from the hill, tribune moves to a handy central post behind them.
LCart PIP5, axis 6=switch right (to centre)Not a perfect answer but general moves up to bring himself and reserves into line, pulls his Iberian Ax in the woods away and uses LH to ZOC hastati.
PRom PIP2, axis 2=remain centreHastati turn to face and tribune pulls back to low hill, potentially menacing LH.
LCart PIP2, axis 1=remain centreTime for a decision! General, Liby Sp and Iberian Ax charge, and LH pulls well back.
Melee: Roman line has to shift, so melee resolves to CvGen (4-1 lapped) v Bd (3-1 lapped). Draw=CvGen recoils as per 3.0 rules.
PRom PIP3, axis 2=remain centreTribune uses the chance to reform hastati on reserve triarii
LCart PIP4, axis 6=shift to right flankThe PRom left looks congested! Cv engage Brutti, then the entire battle line closes up.
Melee 1: CvGen [rnd6]+4 v Bd [rnd4]+3-1 lapped=10:6, Bd recoil
Melee 2: Cv [rnd4]+3 v Brutti 4Ax [rnd3]+3=7:6, Ax recoil (pushing equites back)
Melee 3: Ps [rnd3]+2 v Brutti 4Ax [rnd6]+3-1 lapped=5:8, Ps recoil
Melee 4: Ps [rnd5]+2-1 lapped v Bd [rnd6]+5-1 lapped=6:10, Ps recoil
PRom PIP2, axis 1=remain centreTribune only spends one, advancing hastati and triarii to join the general line of battle.
LCart PIP4, axis 6= shift right (rotates to left flank)Using 2 PIPs owing to woods, the far-left Ligurians slam into Ps, while the general pulls out and uses LibySp to mark Bd.
Melee: 4Ax [rnd5]+3 v velites [rnd3]+2=8:5, velites recoils.
PRom PIP2, axis 3=remain centreCharge! With the second PIP, triarii double. Not that this actually helps, in 3.0.
Melee 2: Bd [rnd4]+5 v 4Ax [rnd1]+3= 9:4, Ax destroyed
Melee 3: Bd [rnd1]+5 v 4Ax [rnd2]+3-1 lapped=6:4, Ax recoil
Melee 4: Bd [rnd4]+5-1lapped v Sp [rnd2]+4-1lapped=8:5, Sp recoil
LCart PIP3, axis 3=remain leftCvGen shifts full left (again, not a 3.0 full move!) and is now in command range of Liguirian Ax. They charge the stubborn velites while an LH element marks the velites so that a recoil will be fatal.
Melee: 4Ax [rnd2]+3 v Ps [rnd6]+2=5:8, Ax recoil
PRom PIP1, axis 6=switch rightNo sense writing off the lone velites - tribune charges LH to put pressure there.
Melee: CvGen [rnd2]+4 v LH [rnd2]+2=6:4, LH recoil
LCart PIP5, axis 6=shift right (to centre)Lots of tidy-up to do with the 5 PIPs. The entire LCart battle line reforms.
PRom PIP5, axis 2=remain rightBoth velites (in order to avoid being recoiled to death) and tribune charge. With plenty of spare points the PRom battle line charges and massed melee ensues!
Melee 1: CvGen [rnd6]+4 v LH [rnd1]+2=10:3, LH destroyed
Melee 2: Bd [rnd6]+5 v 4Ax [rnd5]+3=11:8, Ax recoils
Melee 3: triarii 4Sp [rnd6]+4+1 support v Libyan 4Sp [rnd5]+4-1 lapped=11:8, LibySp recoils
Melee 4: Bd [rnd3]+5 v Ps [rnd 6]+2=8:6, Ps recoils
Melee 5: Bd [rnd 1]+5 v 4Sp [rnd6]+4-2 double-lapped=6:8, Bd recoils
Melee 6: Brutti 4Ax [rnd1]+3-1 lapped v Ps [rnd6]+2-1 lapped=3:7, Brutti 4Ax destroyed
Melee 7: velites Ps [rnd2]+2 v Ligurian 4Ax [rnd2]+3=4:5, Ps recoils
LCart PIP5, axis 4=shift to leftOver in the woods the Ligurian 4Ax charge again, while LH shut the velites in this time. Spare PIPs are spent tidying the line.
Melee: Ligurians with LH help finally destroy the velites!
PRom PIP4, axis 2=remain rightWith an enemy LH and Ax suddenly unlocked, the right looks weak. Time to shift the equites over. That costs 2 PIPs as it is tucked over the far slope of the hill. Hastati charge forward and the tribune closes the gate on the enemy CvGen, in a high-risk move.
Melee 2: triarii 4Sp [rnd5]+4+1 supp -1 lapped v Liby4Sp [rnd5]+4+1 supp=9:10, triarii recoils
Melee 3: Bd [rnd5]+3 v CvGen [rnd3]+4-1 lapped=CvGen destroyed
The tally is 3:3 in terms of lost elements, the game continues
LCart PIP1, no move possibleMelee: Iberian 4Ax [rnd6]+3-1 lapped v hastati Bd [rnd2]+5-1 lapped=8:6, Bd recoils
PRom PIP3, axis 5=shift left (to centre)
Tribune uses 3PIPs to charge, close door with hastati on Iberian 4Ax, and attack LibySp with triarii
Melee 1: hastati Bd [rnd3]+5 v Iberian 4Ax [rnd3]+3-1 lapped=8:5, 4Ax destroyed
Melee 2: triarii 4Sp [rnd5]+4+1 support v Liby4Sp [rnd6]+4+1supp-1lapped=10:10, no outcome
Melee 3: triarii 4Sp [rnd3]+4+1supp-1lapped v Liby4Sp [rnd2]+4+1supp=7:7, no outcome
Game over! PRom win taking 4Gen to 3
I'm really encouraged by these solo tweaks and will be using the same on the next one!