Too late I see as you are off to EB.

But maybe these experiences can help you in EB? Try it out here where we can help you set it up properly and then add it to EB... I think that is a great compromise. We get what we want and EB get what it wants. What do you say?

Anyway on a technical point.
The echelon doesn't work on offense but it does on the defense? Good enough for me, I didn't expect it to work perfectly with the AI. Maybe it is better with the player? Well, since the formations can be set to either defence, offense or both I think it is perfectly ok to remove the offense tag and leave it be at defence.

Oh and a point, maybe set the phalanx depth a bit lower. That echelon on defence was in for a bad beating as the Roman formation outstreched it by a whole unit on the forward part. Not good as that gives the Romans a great advantage. The other phalanxes were not into the battle yet but the first one would be outflanked.

Of course this brings in the hypothetical wedge formation, where we eliminate the weak right flank alltogether.
Such a formation would be close to unflankable by anything other than cavalry, due to its depth and width.