^ That would look sweet but rear visibility would suck :-( ^
As far as performance goes I would mount the spare in the interior's floor board. Definitely looks a lot better with the roof rack in place though. As far as rear seat just leave yourself the option of putting it back in just in case you have a group of people that want to hang on for some off roading.
Could you make some fender flares for this thing? Nothing too crazy kinda like what LDub added to his?