These types of wars seems quite like an exploit to me and the penalties are pretty small, maybe so small you are actaully better of making no CB wars than bother with actually having a CB. Maybe they should be replaced with some sort of prepared war in which you declare your intention to invade Another country and after a month or so you will either have to go to war or suffer a loss of popularity and legtimacy. This give some time for the defender to prepare.