I'm... not sure what you mean. If you mean online battling against other players, that's obviously a thing that exists. If you're talking about implementing those features into crystal itself, that'd require some serious scripting and I'm unsure if it's even possible. If it's neither of those, I'm not really sure what you mean.
Or do you mean some kind of tournament system where every trainer in the battle tower is an online user? That'd be pretty interesting, though it sounds pretty hard to do in as far as coming up with mechanics.