OK, so so far I’ve had an idea of how to build a geared unicycle so that I can use the cranks I want and the wheel size I want and still get a harder gear for riding skateparks. Then, as I’m looking through some threads that I’d looked at before, I realised that I’ve pretty much just thought up what somebody else has already done, meaning this:
Which is to be found here:
http://www.unicyclist.com/forums/showthread.php?t=52571&highlight=jackshaft