Baking Multiple Objects to One UVW Map

Hello All, General Question:

I have an seat object that has moving parts, opening partitions and recline-able seat ect. I was wondering if there is a way to bake the movable objects using the same UV map as the rest of the seat, rather than have a detached armrest or something using a whole new map. Basically i had everything using one map, now if i detach it to its own object it will bake a new map with a bunch of dead space. I just want to minimize any unnecessary extra map baking if possible.

Hope that makes sense, thanks for any help