Regarding trades, can't we suffice it to say that if better value or better fit players emerge in a real trade option then we should make the trade? But in the absence of an actual trade scenario (i.e., someone actually offering a certain player(s) for ours), I go nutty listening to who should/shouldn't be traded. ANY trade depends completely on who/what you get in return and we really don't know how other GMs value their own players or ours.
My opinions:
Shelden is insurance -- a nice player to have on the bench if you need him for foul trouble situation or injury and for spot minutes.
Baby brings a ton (literally and figuratively) to the table off the bench. He can turn games around with energy and offensive skills in a way that Shelden really can't. Another thing that seperates Baby and Shelden is that Baby simply attracts more attention on the court. You have to know where he is, and yet, he still gets his numbers. That's an important intangible that makes him more valuable than Shelden -- and opens up opportunities for teammates.
TA is of value to this team as long as he doesn't try to do too much. Yes, that's stating the obvious, but I think it may be starting to get in his head. He has, on a couple of occasions, begun to reel out of control for a few possessions, and then has settled back -- as if to say "Oh yeah...I have to remember not to do that". If he can stay under control (always the big 'if' for Tony), then he brings great energy, good defense, and he seems to have the confidence back in his hops. I believe that a 27 year old Tony might prove to be more in control than the younger version. Time will tell, but I believe it's very possible (frontal lobe brain development and all).
Sheed is the man. OP is correct about his low-post presense and play -- gotta love his veratility, defensive capability and the depth at the 4-5 that he provides. He is first off the bench in any scenario.
Add Quis back and the options are almost mind-boggling. It does bode for trade possibilities, but not knowing what other GMs will part with (and for whom), the speculation game is too much for me.