I hope that there is an option to house the electronics elsewhere. Sure, there will be some cost associated with HDMI extenders and such, but they are already approving the cost of overlaying brick with stone.

Maybe you could have the designer come up with a faux stone overlay to hide the ugly details that will be visible when the TV is extended. Or, design a swinging door of stone that allows rear access. I'm sure that this detail would be worthy of mention in a design magazine -- which is mostly what many designers work toward.

We had one job where the light switches were around the corner and down the hall because the customer did not want to see any technology.

I did have one giggly victory with a pain in the neck designer. This was in a former fire house from the horse and buggy era with a very complex open ceiling that was painted black (exposed pipes, ducts, wiring, big beams).  We were using four surface mounted (black) B&W 804's as "ceiling" speakers. The designer came into the shop demanding to know when we were going to install the speakers because he did not want us to hold up the schedule. I informed him that we had already installed the "invisible" speakers.