Having 12 prospects is great if everyone has the same strategy.
But for people who want to have an amazing farm system, at the expense of the MLB club, or for those people who would rather have multiple 2nd or 3rd tier prospects instead of a handful of blue-chippers, it doesn't work.
I think 25 prospects is the perfect amount. One for each spot on the roster. Nobody is going to force you to have that many, and in terms of trade, I doubt you'll be spending a lot of time checking out Deck Mcguire. Just have your trade partners highlight their more important minor league prospects if you aren't familiar with them. Generally, I don't look through every milb prospect somebody has if I'm trying to trade with them. More often, they pitch me a prospect or two.