Should players be able to trade in the off-season? Yes.
Should players be able to trade up to the day of the draft? No.
Everyone else needs some time to digest who everyone else is keeping, who everyone else is going to need, and who is going to be available. Our keeper deadline is March 1st. Our draft hasn't been scheduled yet, but it'll be early/mid March, but not earlier than the 8th. So everyone will have at least a week to digest the ramifications of everyone else's keepers so they can adequately plan for their own draft.
As far as trading keepers and picks, I would say caveat emptor. If two guys want to agree, after keepers are announced or on draft day, that they're swapping guys or swapping a guy for a pick or whatever, that's their deal. I'm not going to enforce anything because I'm not going to get into it. I got the draft to worry about. So if they decide to do it and it works out, fine. But if one starts crying that they didn't get what they were promised... too bad.
0-3 to 4-3. Worst choke in the history of baseball. Enough said.