I'm a bit puzzled that anybody could think + on impact is "not enough". ++ is clearly too much, since that is what the situation would be if the thorakitai threw away all of their equipment, turned around, and waited for the pikes to charge them in the rear.
When considering what happens in melee, a few other things to consider...
Anyone using a two handed weapon cannot use a shield in the same way, not just slightly reducing their ability to defend themselves, but they also cannot use the shield in an offensive manner. I suspect this is part of the thinking behind not allowing armoured pikemen.
I doubt the melee continues with a textbook "5 neat lines of pikes projecting beyond the front of the formation and holding the enemy out of reach". Even if the opponents cannot knock pikes aside or break shafts and get in between those that remain in the confusion, a pike with somebody impaled on it may become ineffective for some time. Pikemen did carry secondary weapons as well, and probably not just in case they got charged in flank or rear
The chance to score the first disruption is worth more in this sort of fight than against e.g. legionaries, because it also means more chance of getting the opponent to fragmented, which loses the depth POAs.
Fielding thorakitai as MF instead of HF would make them less effective as primary battle line infantry. There's a whole other debate to be had right there...but I would suggest that if you think HF thorakitai are too effective when comapred to historical performance you should argue that they shouldn't be graded as HF, rather than that (effectively) armoured hoplites are overpowered.
In terms of points per base frontage, 4 deep pikes are 20% more expensive than 2 deep thorakitai. So 24 bases of thorakitai 2 deep vs 40 bases of pikes 10 deep, with thorakitai overlapping at both ends would be about as close as you can get to an apples-vs-some-other-variety-of-apples comparison. I suspect that's advantage to pikes overall - assuming it is 5 BGs of 8 vs. 3 BGs of 8, 3 BGs of pike have an overall advantage (up in impact, even in melee if the impact is drawn), whilst the other 2 BGs are not clear cut...pikes still up in impact, if the thorakitai are disrupted in impact that effectively cancels out the 2 overlap dice in melee and the pikes have the edge (thorakitai closer to fragmentation disaster), whereas if the impact is drawn the pikes are obviously likely to lose over the next round or three.
And not forgetting the lesser chance that the thorakitai can, with a bit of luck, win the impact and then the pikes are really in trouble.
Finger in the air, it feels to me like the pikes come out slightly more cost effective in this confrontation. Not having experienced a similar matchup on the table yet I may be way out of line!
Hmmm...I'm looking for some little coding projects at the moment to refresh my knowledge of certain languages...maybe I should write a little simulator
