Actually there is an 'audi' as you put it. the inferno range. These have pretty much the same reliability as tippmanns and bt's ( i did once drop it in a
river and it was absolutely fine) but it ha one distinct advantage - the bolt out back design.
Basically, most problems with mechanical markers occur due to broken paint etc in the bolt. Whereas with tippmannns or bt4's one would have to take the entire thing apart to get at the bolt, with inferno's, you just have to pull the pin out and the bolt slides out allowing you to clean/relube it etc.
But by far are these markers not the bmw's of the Market. These are just the beSt in terms of site markers.
But I'd just like to point out to you mate that there is a lot to a site, and the hardest bit is the land, permission from the council and insurance.
Look into them, and then worry about gear.
(oh and for the record You can use a 12 or 20 oz co2 bottle mounted on a gun just fine. You don't need to use a 4oz an frankly; remote lines are a pain in the ass.
On a final note, if you're looking for a scenario (real life) look, look at the tippmann bravo and sierra ones. These are effectively tippmann 98's in a new shell.