I didn't read through all the post so I apologize if I repeat something already mentioned.
I would advise against the overhead pendulum style set up. I've been detailing for 25+ years and while they are nice, there are drawbacks too. The biggest issue I saw back when I used them was the hose slapping against the side of the car when users weren't paying attention. This can and will damage the paint finish. The other issue I saw was hoses wearing faster where the lower hose loop touches the ground. Leaking was another issue that came up and its just more parts and harder to get at when needing to be repaired.
As far as pressure washers go I'd suggest staying away from box store units, as you can slam a few beers and piss with more cleaning power then most of them have. Kranzel and CamSpray are some top notch brands, but expensive too. For someone only working on their own vehicle this is a nice option, compact, powerful, and can easily be wall mounted.
http://www.pressurewashersdirect.com/AR-AR630TSS-HOT-Pressure-Washer/p10058.html
I'm currently planning a new additional (24' x 40') and will be making the front two stalls my wash bay. I plan to use moisture resistant drywall and then installing the water proof panels others have mentioned. I will be using ONR whenever possible, but for bug removal, wheel and wheel well cleaning, and winter salt/sand removal, a pressure washer is key.
I will also be wall mounting my CR Spotless system and having it set up to switch over from tap water to deionized for the final rinse, OR I may sell my CR system and purchase this set up instead simply for the ease of resin changing.
http://windows101.com/shop/product_info.php?cPath=74_176&products_id=2445
For drying the car after a traditional wash the Metro Vac Master Blaster is the bomb! With the 30' hose option you can wall mount it and should have no issue reaching around the car.
http://www.detailedimage.com/Metro-Vacuums-M11/Master-Blaster-Revolution-P973/30-hose-S2/
Rasky