Have unowned territories grow. Basically each round the bonus that a wholly owned territory would receive is randomly placed on unowned pieces of that territory. It would be like resistance to invaders until the nation is squashed.

For example in the central America group each turn 3 armies are added. If none of the territories are owned then any one of the 4 places could get up to 3 armies, or 3 of 3 for territories could get 1, or 1 could get 2 and another 1, etc...

If part of the bonus is owned, then the remaining parts would distribute the 3 armies.

A second option could be that the amount of armies received in the bonus could decrease by a percentage equal to the percentage of number of territories occupied.

I think it'd be better if it wasn't linked to the bonuses, as there'd be far too many of them.

An a setting to make incremental Wastelands that increases by a certain amount each round would be interesting, though. Similar to how the Reinforcement cards can be made, but with Wastelands.

maybe a percentage of the bonus would be better.