The problem with nitromethane is that you can't run it for a couple of seconds. It takes a lot of prep and the effects last atleast a minute or so when you use it.
I've had an idea about using 15% nitromethane fuel in a seperate tank on a seperate fuel line. To use it you would turn the normal petcock off and the nitromethane petcock on. The nitromethane would slowly mix into the floatbowl and then end up in your engine. When you turn it off however, it takes time to clear the floatbowl of the leftovers.
This whole setup poses a few problems:
1. You can not turn off an engine when it is running on nitromethane. Even a little amount of the stuff will cause the engine to selfcombust. So if anything goes wrong or you need to stop, you have a HUGE problem.
2. You'd always need to run lead-replacer, special 2-stroke oil and octane booster in your normal fuel or the nitromethane would arrive at the same time as the additives, leaving the engine unprotected for a short period of time (As the nitro would burn but the additives haven't bonded to the cylinderwall and piston yet.).
3. I wouldn't like to sit on a moped that has a tank of nitromethane strapped to it. Gasoline fires can be bad, but they are a candlelit dinner compared to a nitromethane fire.