I know, it's like beating a dead horse, but it's always worth a try since we all know AoC has the best foundation for PVP when it comes to MMO's.
It would be interesting to see Funcom deliver a F2P Client that is designed purely for PVP Mini Games and Sieges only with a Item Store attached with it. You're allowed to unlock and create 1 level 80 character for free and at pvp 5 with a bunch of AA unlocked. You get a choice of unlocking 2 mini-game maps and you would have to either buy maps from the in-game store to unlock them or subscribe to temporarily unlock them each month you pay for at a cheaper price of 4 bucks a month. Players can buy cosmetics that make them look cool, since we all know AoC has the best oufits and style out there or cool little items like a smoking pipe or stylish skins for your weapons like you see in cs:go.
Players only download a client for the mini game maps and siege locations, this way it's only a 2-4 gig download instead of the 32 gig download. There should also be a ready room in which a player can visually check out his toons appearance, buy items from the Auction House that may be useful for PVP. Example would be the PVP Armory that already exists.
For sieges, players can sign up when they're available if guilds require a ringer to fill in or have public mode sieges that happen once every 2 or 3 hours with a smaller group. 24 vs 24 would be more feasible due to the server lag with smaller siege castle that is more static and cosmetic like Khemi or Tortage.
This would work if Funcom saw the promise in it. This idea is better then "arenas" because you're tapping in to a pure pvp market that has proven to work over and over again. Look at League of Legends, CS:GO, Smite and other jump in jump out team play games.... This is the future of gaming and it works.