Interesting the different ways we do it.
I run a void around the slab for brick veneer work.
For an even height rebate it is best though, it does get more time consuming if you have deepened rebates all over the place.
I see your reasoning for doing it this way. I presume it would reduce the slab volume accordingly if estimating.
And I don't know if you can, I expect it is possible. I will let one of the maestros chime in with that one.

you could try placing a void Inside the panel family, however I am not sure it will gain you much because I am pretty certain you will still need to cut the geometry from your slab in each case (ie it wont automatically cut the void out of your slab). I could be wrong but that is my initial thought on it without having tested it.

For this kind of cutaway from a slab I tend to just do void sweeps insitu which are fairly easy to manage and quick to do on a per project basis.

You can try adding a void to your panel family, however my next question, is the panel actually a family?
What family is it?
If you use generic walls as this PC wall panel, then I'm afraid you can not add a void to it.
Walls in revit are "system" families and as such you can not edit or modify them.

A solution would be to create a component family to use in their place, and you could add your void this way, and if you make it a "generic metric" family, hosted on the slab, in this case your void would cut your slab automatically for the recess.

Slab edges might be easier to edit, and voids sucks bc they are so invisible.