I'd say the best way to get the arena APs is to get in a party and just farm arena for long periods of time... the APs come naturally when you do that. I farmed for about 5 hours with a guy who had no arena APs and by the end he had almost all of them except for challenger and the spider AP. It's far harder to just go in and hunt the specific AP. All of the current arena APs can be achieved in the new arena so no need to bring back the old one