Some pretty serious fabrication involved there man... you'd need to be pretty competant with bodywork and interior to pull it off. The other thing youd want to make sure is that the latches are secure enough to prevent it being a way ppl could break in, and that it was a good enough seal to stop water getting in, because it wont have anywhere to drain.
I'd just save and invest in the sunroof if you're keen, or go the WRC roof scoof FTW!