The s85 would respond to boost extremely well, even in totally stock form. High reving high volumetric efficiency motors can get some amazing numbers. There are tons of 500-600whp Hondas running around with completely stock engines. A "street" turbo kit on a Honda S2000 makes 400whp easily on pump gas at low boost.
But yeah, the space. I'm sure with some cutting, welding, and work, you could make it work. If I wasn't afraid to cut the hell out of my car and had an extra M5 worth of money burning a hole in my pocket I'd turbo my M5 in a heartbeat!
Turbo S85 V10 in that upside down country, sounds amazing!
https://www.youtube.com/watch?v=Myrep2aIgbw