I don't understand why the threat of Aybar being traded should make you drop him.
First off, I think you have a very good minor league team there. I'd have to say that if you don't drop Marcus Sanders, then you shouldn't drop anyone. I don't think that Sanders will be able to get on enough in order to play in the majors. And its not like he is a defensive wizard at 2B. He's also pretty far away.
I wholeheartedly agree with you on Carlos Gonzalez; he should be special. Pence has too much raw power to drop, although I have a feeling that as he moves up the ladder, he will have problems with making contact (more than he already does).
Just my opinion, though.
If you have a league that uses two catchers with 20 teams, I might put Salty above one of these guys, but in a 12 team league with one catcher, I think you stick with the ones that you have.