[@Vetis] Hey! We've just started a new arc in Vareena Town, so good time to join. Your character could be at the gym, annoyed that the leader isn't there.

You can have Pokemon from any gen, and while nobody will be catching legendaries, a temporary team-up with a legendary or mythical much, much later down the line is certainly possible. If that's what you'd like, just let me or Heckno know and we'll discuss it together :)