The way the Go gyms are handled is quite unique. It'd be tough to manage a similar way here by creating a battle mechanic in a similar way since its AI controlled. You also wouldn't be able to rely on that person or that group to be able to just jump up and be ready for battle. So I feel as if the Kanto battle style (pre-set) would be the easiest. If you went to attempt a Go style one (maybe just one on the side to test and see what we can come up with) then that sounds good too, but as for a main event? The Kanto gyms sound great to me.