Potential complications running data cables
The problems you are trying to solve -- so is everybody else.  There are a lot of consumer products on the market aiming to solve the "how do I put my TV here" problem.  Their "universal solvent" seems to be ethernet or WiFi.

You're saying pre-run all the above wires to an appropriate central place - somewhere a wife would authorize a bunch of tech gear to be stacked up.

I wouldn't do that.  I'd run the fattest conduit you can manage.  That way you can pull any cable that may be required in the future - Cat7, Lightning, USB3, whatever. 

Coax (I assume you mean RG6 cable TV coax) generally implies RF frequency.  Two Coax devices can drive into each other without incident. 

RCA (which is also coax)  - I would not expect two outputs to damage each other since their output is line-level.  (a line output against a phonograph needle output - different deal.)  Anyway that makes me laugh - I haven't used RCA connectors in AV for over a decade, except obviously for line-level audio, and that doesn't like going a long distance. 

Ethernet will be fine.  Plugging nose-to-nose happens all the time when you use a regular cable when you should've used a crossover cable, or vice versa. 

HDMI is negotiated. But HDMI is not going to work over any kind of distance, and you have a lot of gratuitous distance going to the concentration point and back out to the other room.  Also several connectors.