Now that I think of, yea, the AI is pretty braindead. They're simply not capable of any advanced maneuvers. I never tried it in a custom battle, but I guess H. Peltasts go down pretty fast if you charge them from behind.
Anyway, I hope you manage to find some kind of compromise to get things balanced. Of course, one can put battle difficulty on hard or vhard but since we know RTW has a simple bonus system for that, I kind of prefer medium for B difficulty.
I've read all the stuff you posted about the advanced weapons before I even downloaded the mod. Interesting stuff. Can you point me to a source where you got that? Specifically the double bows.
Also I remembered something I wanted to suggest to make things more interesting. Maybe you could make the Libyan (I don't know how I managed to misspell it
Lybian previously!) more spicy by spawning armies of Egypt and/or Greeks right next to them if the player selected Libya so that you re-create the chase that is mentioned in the lore ("hot on their heels"). Just a stack or two not to weaken the Libyan horde too much.
Oh, yea, one last thing. I don't know if the Lore and weapon tech texts come packed with the mod. If not, you should include them in a "documentation" folder or something...
So long for now. Happy modding, I hope I helped.