I'm so excited for the DDR tournament and IIDX and Pop 'n would be awesome as well if those happened.
Actually, we should talk to Gosha and Pantsu about Pop'N; they both have really good ASC's. IIDX could be done, but the skill gaps between the people who would be playing would be hueg.
Stepmania tourneyXD
If there's a DDR tournament, this will probably be how it's done. That or using DDR 5th Mix through MAME if there's a legal issue (I know someone with a 5th Mix ROM, so it would be 100% legal, while StepMania would be somewhat questionable).
If I'm providing the StepMania, I intend to have a contract written that will make it a fully legal application. This is possible because:
1. Kumoricon is technically a private (member-only) event, not an event where one purchases admission, so StepMania is perfectly viable as long as the bylaws are still phrased in a manner that specifies that registration is for Altonimbus membership, not for Kumoricon admission.
2. It would be on free play