I like your thinking, but you may need to find another closer to be in a position to trade saves later ijn the season. You have three excellent closers, but in a league of that size, there will probably be other teams who can compete with you in saves.
I love the idea of both Blalock and Teixeira on one roster. With a bit of luck, Blalock might even be your answer at 2b.
For that fourth starter, I wouldn't make a move just yet. Benson might be just what you're looking for...
Looks like you're in great shape!