I think you're on the right track, I have a friend who put a set of racing seats in his DD/WW car and it ruined the car from a DD standpoint. Stick with the OEM type seat and harnesses, I think you'll be golden.
I'll see if I can find them, but that same friend has a set of DOT approved harnesses that a central unlock that is the same type as your factory belts...I just can't remember who made them right now.
EDIT:
THESE are not the ones I was looking for, but are the same idea.