A version that I came up with years ago, playing the board game RISK, was to have the option of being able to get your armies the normal way that we are all used at the beggining of a turn. Or being able to cash in a certain amount of your owing armies to put an 'ENTRENCHMENT' card on a particular country. This enabled each army on that card to be able to fight with a plus 1 die roll. (while they where on it)
We also experimented with having capitals in each bonus area, this was the only place that your armies could spawn from. On your next turn you could move them. So, to add more realism and tactics, for instance if you spawned say 20 armies from China, you could move 5 to Mongolia, 5 to Taiwan, etc etc (example world 2.0). Or you could have the same option but be able to use them on the same turn. It would lead to some very interesting playing. And it creates a few interesting questions when it comes to team games. But nothing insurmountable.