XPand kind of has a season doesn't it? Could operate outside of that. I think it also has the element that teams can play any time for a kind of perpetual ranking, IIRC. Probably don't RC though.:lol
I remember doubles being reasonably easy to organise, although in fairness TCK did most of it after the first few matches. But XPand was a pain because people seemed to have lost interest. It usually ended up being doubles races most of the time anyway, due to availability and the fact that there were some teams with only two players anyway. That's really the key - people just need to think before they sign up and make sure they'll participate and are willing to organise.
Another option - do doubles for a certain period. Then join up doubles teams based on their final positions at the end of that period to make XPand teams so that you have very balanced XPand teams and people can race with new folk and get to know people they wouldn't normally talk to. (Yeah I know, no-one will like this option).
One more option ( I most like this one) - don't predefine teams at all. Just do weekly doubles events like the ASTRAL events used to be. Everyone signs up ahead and is paired up. Up to say, 16 players total? They race in two pools, and then do a winner's pool and, er, not-quite-as-win-ers pool based on final positions in the first round. Basically ASTRAL but with doubles. Maybe that's what kaori was getting at earlier? I seriously think the less organisation the better, and that way people wouldn't have to commit to a long term league either. If they do two races and then can't be arsed, then it can all just roll on without them. It'll be a whole different thing each week too - less predictable. You could always do it for a month and then get the top 8 players to face off in two doubles semi-finals and a final, or something like that.