It should come with some kind of minimum limit though... otherwise this would be oh so exploitable. Putting a 10 man unit in an undefended enemy region shouldn't prevent recruitment. Only a sizable army would be able to manage that.
I understand the principle of a limit (taken to an extreme, just dropping 1-men limitia everywhere would be abuse), but I can see it working with the limit being quite small. We have looking for solutions to make small armies desirable over large blobs for some time, and this is a very good example. A scattered army would be able to effectively 'occupy' a territory, as in denying its military use to the enemy, temporarily without immediately resorting to long and costly TOs.
1 men per 200 population seems a reasonable limit. It would set a minimum occupying force at 30 men (a small unit) for a typical 6'000 people rural, and accordingly higher limits for townslands and cities.
