The Stair of Destiny (Sanctuary) is in Hellfire at the Dark Portal. It would be a nice place to allow duels since many horde and alliance fight in Blasted Lands. I see many verbal disputes where 1v1s aren't possible without interference.
Allowing players to duel at the Stair of Destiny would just be a nice QOL feature for WPVP.
A dedicated duel spot is one of the great features of Blackrock.
As a Blackrock player who's leveling a char on Lordaeron, im voting with 2 hands for this feature. Whether it resets cds or players disappear is up for discussion, but i think other realms surely can use a place for duelers.
I was surprised on Lordaeron that the gates of SW and gates of Orgri werent really a dueling spot.
If a duel spot was to be implemented on Icecrown, the easy solution to the cooldown reset exploit potential is that all of your abilities go onto a full cooldown if you leave the area, and all buffs are removed. Kind of the reverse of what happens when you join an arena. I don't see the difficulty in mitigating any unintended consequences with this.
Do you accept custom suggestions? Out of my imagination, below the wyrmrest temple there are unused portals, one of which could be used to get to a custom instance like the Emerald Sanctum or the Bronze Sanctum or something similar, and be the duel zone. There are old files with emerald dream assets, something like that could be used.