My NuTone fan says that it's UL approved for over shower use when wired with GFCI circuit. Would it be acceptable if I ran the fan power wire first through a plain face (non-outlet, but outlet sized unit) GFCI unit, through the switch and to the fan with nothing else on that circuit? I know that I could probably run it after a GFCI outlet but I like the idea of it being on an independent branch with it's own protection. Thoughts?

I don't see why not. I would want to use a GFI circuit breaker, but maybe you are still on fuses.

At the present my panel is getting filled and I can't dedicate a single space and breaker to just the vent fan, That is why I am trying to arrange a way to tie it in to the power supply as it will be distributed to the new fixtures and outlets.

Thanks.

Check out half size breakers. Doubt they come in GFCI, but swap stuff around. I added a few in 1977, and no problems since.