Tom,
I think you should go for a 3 club format. As was said earlier, they're quite popular in the UK&I and Sweden also.
I wouldn't be interested in a 1 club competition myself, but I would play a 3 club game. I just have no interest in using a 5-iron (for example) on the greens. At least with a 3-club format, you can choose a putter, a mid-iron and a 3W for example.
If you're concerned about the turnout, then go with 3 clubs.
Dónal.