Forget collective bargaining agreements and stuff like that. If you were deciding from scratch the number of players each major league team should have, what would you say? Is 25 the perfect number, as perfect as 90 feet between bases?
I definitely wouldn't want to expand the rosters and allow for even more specialization. In fact, I'd like to encourage more two-way players, from Babe Ruth to Brooks Kieschnick.
On the other hand, I don't want to contract the roster too much and have arms fall off. And I really enjoy watching managers make moves - I actually do "pay to see managers manage." So I don't want to rid the game of difficult decisions.