First off, I will start by saying that maybe I am misunderstanding what the intention of having custom arenas is. I was under the impression that they were being implemented to strengthen the sPvP base and to provide more ways for sPvPers to form teams, do tournaments, etc. With gems being involved it just kind of makes the whole thing seem greedy.
What I was thinking was 2 possible things.. One is for GLORY to be used somehow either in the purchase or maybe just in the upkeep of the arenas. It would of course be a large amount of glory needed and could be traded in for upkeep tokens or whatever they have at the gem store.
Another option which I like better personally is to give players the option to turn their glory into gold. Then the hardcore pvp’ers will have a way to use their glory to get gold which they could use to buy gems to get tokens or kits.