I say its theoretically possible, but would require extremely major modification of both ESXi and the fglrx drivers, so not something you could just make some instructions for. I am curious as to why you would want to do this. I am also missing the connection to reusing the server for headless Windows server.
I would think it would take a professional coder much more than 20 BTC worth of time to complete a project of this magnitude, even at the all time high BTC/USD exchange rate.
I do, however, like your thinking because sometimes it is unconventional ideas like this that spur innovationa and development.
BTW, are you the guy with the youtube videos about silver?