imho catering is overkill. having one or several fast food stands/sandwish bars/... around should do. maybe just a fridge with some drinks but even that is optional if there are vending machines nearby.
also, as you said, having pubs around is a must, and working wifi is very useful. But if you pick the location cleverly (or decide to go with a bigger conf), all of the above becomes a lot easier.
About the froscon idea: I think it pulls away some attention from Arch if there are too many other things to do, and it's less "cousy" but you get a lot of advantages (logistics taken care of, maybe some interested people stopping by). I don't know what you're referring to with the froscon organising complaints though. Maybe Roman's issues with the visa, but that's a problem with the german embassy, not froscon (afaik).
What makes an Archcon an archcon, and not "arch devs present at conference $foo" is mostly Arch talks. lots of Arch talks, but I think that won't be an issue. If every dev I'v met so far at froscon/fosdem gives 1 presentation, you can easily fill 2 days :)
Anyway, since the froscon this year is next weekend, this may be a perfect time for some of our devs to discuss further and maybe get together with the froscon crew. we would definitely need a much bigger devroom then the one we have now, but that should be mostly it. Unfortunately I won't make it to froscon this year :(