I did come up with a set of rules for a 'sportsman' middleweight. As there seems to be alot of feather people wanting to get into the heavyweights, but its too big of a step. Quick rules that i came up with:

Max 400watt drive motors (wheelchairs ect)
LP pneumatics only (regulator mouted directly onto co2 tank)
No Ti
SLA batteries only (maybe allow nicads/mimh)

Thoughts? It would be a way of feather people moving up, without some of the risk and trouble of heavys, by limiting components will keep the costs down.