Adding arenas would be very entertaining and beneficial. I think the abyssal filaments is the way to do it.
Each filament can be unique offering different set of rules such as how many ships per team can enter, what meta modules can be used, type of modules can be used, ship type, and so on.
The arena filament would act the same way as the pve filament in terms of ship loss. If you lose your ship in the arena, you lose your pod as well. This could make fights more fair since the threat of losing implants is greater.
There could be a rating system, so players with more skill will fight similar skill. There could be a reward chest that can be looted at the end which will also open the portal to escape. There could be a timer that will destroy the weakest ship(s) at the end.
Arenas would offer instant action, could be more about skill instead of bling because of the rules, and be a great addition to the game.
Yay. More arena stuff. That is exactly what EVE needs.