Just shooting this out there, so tie me at the stake and burn me, or let your inner gladiatorial instincts smile at the prospect of blood, this is my idea:

What do you guys think about an underground, or public coliseum that all factions may enter for PvP? Highlander type events would include "X" amount of faction members, from all factions, fighting in one arena until there is only 1. Domination events would include all three factions, but team oriented based on a particular legendary battle, that the players would enact in bloody combat until one faction emerged victorious. Environmental events could involve either team oriented or every man for himself, with the inclusion of random creatures from the game that is against anyone close enough to attack.

Winner(s) of the events could be awarded gladiator tokens that can eventually be used to purchase PvP gear. Leaderboards could reflect champions of these events that are etched into the "Halls of Champions" that are persistent, and last until the last days of ESO. I think it would be cool, but I'd like to hear what you guys have to think or even post your own suggestions.