JGTC cars don't have to be homologated. The new 350Z JGTC car for example, has a twin turbo V6. They still have Supras running in the series and the car has been out of production for a while now. They used to run a turbo inline four, and now they run a normally aspirated V8. So yeah, Honda could run some kind of wacky NSX with no need for a homologation special.