If the motor made more more TQ than the jet required at its maximum input rating, it would mean that the jet would be operating at an rpm above its rating and outside its performance/efficiency envelope. Such condition was experienced with the Hamilton HJ212, the impeller absorbed the power but the jet yielded zero performance gain...the extra horsepower was wasted in cavitation and impeller reversion.

Sure you can use a 600 cid engine, 6.2 Raptor 575, 6.2 LSA, 6.2 LT4, 6.2 Hellcat, 632 Haxby Chev, etc...none of these engines exceed the 1200hp rating of the Scott 912. Running more cubes would allow more intake vacuum at a given hp, and not need the octane of a supercharged engine. If Scott comes out with more progressive impellers for their 912 jet, I would consider a swap to a 550hp Cummins QSB6.7.