I can see how missions could get annoying. I suppose at times you just want to sit back, take the occasional provence and see how things turn out - or expand in your own time. With glorious achievements in MTW you needn't expand much if you didn't want to. But if you have generals rebelling (or worse) because you don't want to capture yet another chunk of land or wash their socks or whatever, then it might become annoying. Hopefully missions will be much easier to mod this time around so people can adjust them to suit their playing style if need be.