Kawasaki's H-2, also supercharged, does more with less. A supercharged 2.1 liter is loafing at 250 hp. A good development program ought to be able to take it well north of 500 hp.
Hesketh has been making small numbers of bikes for a long time now. There is at least one at Barber's museum, maybe more than one. Both of the supercharged Kawasakis have been on display in the entry.
FWIW, I like my ZX14R better. Better riding position. 200ish power before any additional work. Less than half the price of the street version imof the H-2.