I would definitely join. To be honest, though, I'm a little tired of getting raped on Blockbox. Nullpo is almost as fast (and instant DAS is coming, yeah?), PLUS it has support for spins and all that, so if there is something that could be done to flatten the speed curve a little (small ARE or line clear delay, perhaps), it would probably encourage more players to participate, myself included. I'll play either way of course, but I'd rather have fun doing it...
Edit: It could be fun to do it in a little different format, too. Here's one idea: Play a sequence of rotating-participant FFA games to seed the bracket with. At first we may not have many players, so maybe 3 player FFA or so (rather than everyone at once). Give points based on people's placements which are used to rank them in the bracket. Ties can be broken by the rankings of last week's tournament, or just a single FFA involving the tied players. This wouldn't necessarily be a true round-robin, but the goal is basically to get the players warmed up without winding up in a situation where one player is dominating the FFA for many games in a row. I was thinking to rotate players in and out (like, with four players, you'd play: ABC, BCD, CDA, DAB) but I don't know how you would decide how to order the players. Anyway, just a thought.
(Actually, I kind of like this and would like to try it. If we order the people for the seed round by the results of the last tournament [new players or people who didn't play last time at the end; dunno how to sort them - order of signup?] then in the seed round we get games between people of close skill. This could give the lower end players a bigger chance to seed high, though, so if we use these results to instead modify the turnout from the last tournament, what we get is people who do well in the seed round move up, ladder-style, in the seedings. The larger the FFAs, the more games get played for each person, the greater the chance for them to do well and move up or down a lot in the seeding.)
Let's say we had 6 players, A-F. A got first place, F last place. We decide on 3 person FFAs. We play 6 games: ABC, BCD, CDE, DEF, EFA, FAB. If each person got a 1st place, a 2nd place, and a 3rd place in these games, the seeds would be the same as the results of the last tournament. But if, say, player D got three 1sts, he would move up a place or two. Note that this arrangement gives the first N players an advantage, because they wind up playing against the tail end for some of their games, but I think this is OK. The winner ought to have some reward, yeah?