While there are 60 GHz wireless solutions for HDMI connections between sources and the television, from various companies (I just last week saw one at Costco from Vizio) they still require AC power and HDMI connections to operate. And while good - they often are not perfect.

I'm not sure I understand your concern regarding patching the plaster walls. If you don't feel comfortable doing it, hire an experienced professional AV installer. There should not be any patching (usually) in running a drop within the stud cavity from the television to the equipment.

You already have to run electrical for an outlet up there for television AC plug-in anyway.

You can also use wire-mold covered plastic channeling, painted to match the wall, to run all the electrical and AV cables down the face of the wall.

As far as hiding the equipment - no problem - use IR extenders with the receiver mounted at the television, wiring run down the wall, and repeaters in your equipment cabinet.

This really is a very common setup that you, with a little basic instruction, or any qualified installer, should be able to handle.