Sandbox is actually the one world where testing wouldn't help, since countries are automatically removed after 60 days.

I think it might be tricky to implement on a world by world basis, too, since the change is very fundamental to country ownership. In the end, I can always take that route if need be. If I make it a per-world option, then I can enable it in the next new world and see how it plays out.
I think the existing worlds are very much suffering, though. I can certainly understand players getting bored or just deciding they don't want to play anymore and leaving, but players also seem to be quitting
constantly whenever they start getting into a battle. (Just watch the YouTube videos and you'll see country after country pop away once a fight breaks out.) When that happens, the other country (which was likely larger to begin with) simply gets an open path and more land to grow even more. The constant giving up makes the game far too easy for the big countries. The game was supposed to be about war, not about drawing lines and grabbing pixels.
I think letting someone else take over could keep the worlds
far more dynamic, balanced, and interesting. The Zanzabar example above is exactly why I think this change is badly needed.
I'd like to continue the discussion, though.