My fiance has said that having a whole spit roast is a tradition back in the area of Russia where his family comes from.
We're not going to do it on the day, but since we'll have lots of family over from abroad who will probably be here a couple of days, we are seriously thinking about having one the day after the wedding. But we'd do it the proper way, i.e. buy a whole animal, sheep or pig and roast it on a spit over a flame pit.
And just serve with salad and potatos.
I don't see why you couldn't do it on your wedding day, and it would be a good centre piece. But you need to have good quality bread and a good selection of proper salads, not just coleslaw. Greek salads with feta cheese and Russian salad with egg and others, and proper chunky bread. Not cheap rolls. If you work along those lines, it would be pretty classy in my opinion.