The problem with the Late Achaemenid Persians is it horse are undrilled.
But you only have to have 12 bases Heavy cavalry and 6 light cavalry and the rest is up to you.
Early Achaemenid Persians is probley a better army
Drilled Heavy infantry Impact or mounted lancers does seem to be the way to go, Because of 113page, Cohesion test last one on left ANY ONE OF... it did make a great different in my last game.
Mabye it just Dave's bad dice
(Drilled) Romans , pike armys, cavalry army with loads of lance and bow?
But I think
just pick a army you allways wanted to paint and just have fun
All armys have good and bad points, you just have to learn how to use it well
Classical indian's with most of it Troops Drilled sound interesting which i have in 10mm, it will have to join the que for painting