There was a similar sort of pvp/1v1 style combat in XI called Brenner, however it was confined to a specific area (an island atoll iirc). There was also open world group pvp in zones, Ballista. That had a limited window to apply to join via talking to a NPC and then after the window was closed, only those who joined in would be affected. True it was usually nation vs nation, but even if you weren't aligned with one of the nations involved, you could still join in.
Personally, I don't like pvp from my experiences in DCUO and SWTOR, but there's obviously a desire within the community for it. We already have the Wolves Den and Frontlines... have something similar for 1v1. I'd prefer having a set area for it though, not just any open area.