UV problem

hi everybody, i have a bit a special case of uv problem i think:O

i have 3 objects which “overlap” each other as shown in the picture, now the thing is that these objects will be used for a simulator and i need to save as much uvspace as possible.
when i unwrap each object i will have the overlapping parts in more than one texture which costs me a lot uv space.

any tips or tricks how i should approach this?

would it be possible to have the overlapping parts in a seperate texture so each object will have a 2nd texture for the “overlappings” or would such a thing cause problems?

the other problem is that i need the texture seamless from one object to an other:O
is it possible if i bake out my material on all the objects to remove the seams with a projection paint or so?
is it possible to use the projection on multiple objects?