I just don't think the NFL model works in MLB. The games are just too different.
They can't keep doing the player churn that you describe above - rookies don't tend to be on a level field when they start playing, like they can in the NFL. Teams need to invest in them to get to a point where they're ready to compete. Veterans are vital, and can't just be cast aside. Plus, the union is too strong, and non-guaranteed contracts will most likely never happen.
I agree the games are vastly different, although I think the stability in the NFL is adequate, it's not like entire rosters are turned over year to year. I worked in minor-league ball for awhile....and you are right it takes a lot of time for guys to develop. Although I do think at times MLB is a little too slow bringing guys up. Part of the publics problem with it, is that college baseball is nothing compared to college football and so many guys go straight to the minors from HS, that nobody knows who they are until the arrive in the bigs. Just the way it is.
And chimps, did I strike a nerve?
