For the BF merchants, if just one is moving, you can keep Alt Tabbing until they exit out the other side of the obstruction.
Alternately, there is a way to reset NPC locations: Teleporting anywhere (via hex editor)
In acts 2 and 3 there can sometimes be small gaps in the north west corner when two walls meet, which you may be able to toss a teleporter stone through.
You can use the technique in the topic armory trick in act 1
to get a summoning doll through a wall, and have it enter the BF to get your main characters through when you leave the BF.