Don't carve out cubbies. Have them open the entire wall up and reframe (headers like a door way etc) it leaving a large opening almost the size of the TV. Then have them build a plywood box to finish off that space. Use a full motion mount so you can install and service your equipment by pulling the TV out from the wall.

This gives you a large open space so you dont have to fight with each device. My guess is that the contractor would spend the same or less time doing this vs trying to make cubbies between the studs.