When testing maps I have built I always let the AI buy for me. Saves a lot of time and "you have to work with what you get".
Been a while since I logged any games at the Blitz but at times we used to let the AI buy the forces. I liked it because to a degree it eliminated the "cherry picking" of the best gear that is common in PBEM. The drawback was that games tended to be only 19-20 turns in length (could not set the timer yourself if you let the AI buy for player 1.