I would like to be able to quickly view the solids I am working on in a shaded view with other related solids as wireframe or dimmed (translucent).
It is not something I would use every day but would be useful for complicated parts.
It would be similar to the way non-active parts dim in assemblies when editing in place.
It is possible to do this at the moment by selecting a clear body appearance but it means a lot of mouse clicks.