Let's say cross-gen transfer worked like the Time Capsule in I-II for every gen up to now. You can take mons in old gens back to those games, as long as they don't know any new-gen moves, however if they learn a move that was already in those old gens, it becomes legal. What would the competitive meta of old gens look like? Would any mons get something new that significantly changes how good they are in an earlier gen?