It'd be a radical change for baseball, but I wonder if the lack of deadline activity (due to parity and the addition of more playoff spots) might be offset by the idea of letting players go out "on loan" to other clubs similar to the way things are done by soccer clubs in Europe.

You probably wouldn't see a lot of pitchers move (due to the inherent risk that they'll be abused by a team that doesn't have to worry about long-term implications) unless there was lots of fine print regarding compensation if an injury occurs, but it could open up activity for position players mired on basement squads.