on topic, i don't really see a need to seperate the lipos and nimh batteries into different classes. the power advantage is to nimh batteries at our track we run a 13.5 class and mix the two batteries, i have yet to be out powered or beat by a lipo, we also run 8 minute heats and mains. the lighter weight isn't that big a deal IMO, and roar could always keep min weight the same.
i also believe on the club level the 13.5 has an advantage over a stock motor, however at the bigger races with the level of drivers and motors available to them a stock motor my be better.
roar could also drop the stock foam class to build the stock class overall.