Worlds with Predetermined Countries are not set up to resign users. The idea was that each player gets one country and then that country is permanently taken. (I may reverse that and turn the normal 31 days of inactivity rule, though.)
Players joining and never playing has always been a big frustration in the game, though. So, in all worlds, I think I'm going to change the game so that a player must visit the game at least one time in the first two days it begins (or return at least once in the next two days after joining). If not, the country will be resigned automatically. Then, the normal 31 days of inactivity rule takes effect.
The other idea that came to mind was modifying some attack rules for treaties. It's one that I think would make players more careful about if/when they break treaties.
If country Alpha breaks a treaty with country Beta and then also attacks Beta with collateral damage, then Beta would be allowed to attack Alpha immediately. Alpha would still have to wait for the treaty to expire. (That rule wouldn't take effect if Beta attacked Alpha after Alpha broke the treaty. In that case, it would just work as it does today.)
I'm not sure how I feel about that one. Just something that came to mind. Players would have to be more careful about breaking treaties, and it would prevent one country from going from being in a treaty to being the aggressor before the treaty expires.