I think it's only fair that 2fort and Gold Rush get used since Valve Maps players are going to know the other maps a ton better in general. But that's only if we hold a season. I think a straight up tourn will be too short to DEFINITELY include these maps but they should be more heavily weighted in any randomization process.
Duplex, I think that twice a week will be too much for some people. I also think the "when" of us playing these matches is going to be a big problem.
Our first option is to have matches on a set date and time. This makes it easier because we know when each match is being played far in advance and makes life easier on DF. The downside is that scheduled matches (on weekends) might not be the best for some people and we may not be able to get everyone together. The other option is to schedule 1 match a week and let teams play whenever they can both organize at any point during that week. The problem with this is that it makes things very hard on DF as far as the overseeing things good. An alternative is finding some other private server space for this tourney but I don't know how realistic that is. Scheduling for the weekend is probably the lesser of two evils.
There's also the matter of team selection. We haven't really discussed it yet but I'm assuming that people will just make their own teams by getting together and asking. The people left over will either be randomized into their own team or be alternates. There are other options like complete randomization or drafting, but in randomization you might not get to play with the people you want to and a draft would take forever.