Four episodes? I don't see why a body swap story should last more than sixty minutes. After a while it would get a bit tiresome, and the audience would start wishing for the crew to get back to normal.
For maximum enjoyability, how about
Picard <--> Guinan
Worf <--> Troi
Data <--> Riker
Crusher <--> LaForge (I'm sure someone can do better than this lame switch.)
Worf <--> Barclay
Wesley <--> Spot