I'm definitely in favor of having this as a new, symmetrical, but optional win condition. There's also a precedence in earlier games, in Civ4 you win by domination when you have 30% **lead** in population and control 65% of the land, of course numbers can be refined through feedback (sidenote: Civ4's conquest victory is closer to Civ5's domination).
As the OP pointed out, there are countless benefits. AI can actually achieve this, it makes nukes (and razing) a very strong tool in winning the game, the military civs can still be threatening when they're on the other continent etc. etc.
I would also like it as a fellow human (needs citation), opens up a less-grindy, let's bring in the apocalypse path to victory.
It seems a whole lot easier than making AI properly follow a domination victory, just make them more nuke-happy and that's it? (aside from coding in a new condition, which may or may not be harcoded. in that case this can replace the domination victory/or co exist under the same condition, still optional)