An AI will always accept a city gift anywhere on the map as long as they have 3 or less cities.
One thought I've had quite a while, just tested it and it works... in theory. For what we know now, we might need astro, or even paratroopers to reach some of the AI. Seems possible as the requirement is conquest or space. However, if we gift this city to a far away AI and this AI expands more in our part of the world, then we can gift him a ton of warriors, declare war, kill the warriors, raze all but one of his cities here (last city must be threatened) and get a city from the other side of the world in a peace deal. I tested this and managed to get a city I had never seen, which was on another continent together with the capital of the AI. However, it required a ton of war success, killed 40 warriors and razed 6 cities without losses... But I'm not sure what else factors in. I think length of war might be a factor, probably power rating and other stuff. Possibly land and population (i my test I had 2 cities and the AI had 4 when I got the far away city). If we did understand this part of the code, we could figure out if this could be done somehow.
Probably not worth it anyway, getting a city blind, which might be in the middle of the tundra, doesn't necessarily speed up conquest of another continent very much. Except maybe if AI is behind mountain range... Just throwing out whatever ideas I come up with. In any case, first get those exploring workboats out and hopefully we can reach the AI in easier ways.