I wasn't so much thinking about the historical, as the EUII game effect. It meant you could march into a colony in your sphere, without a DOW, and take it. Granted, in the game it was mostly a "shaft France" mechanic, except for a few S Am provinces where both POR and SPA had claims.
But my point is that it did limit colonization by area, and that something like that might work here. I rather like Seli's post.
You miss the point. Colonial demi-wars were frequent in this period, and DID NOT entail the powers involved in a full war. England managed to be allied, at times, to both POR and NED, while still going after their outposts in Asia. That is what we're talking about.
Although making it easier to win a small victory would be good,in general. It shouldn't be necessary to conquer an entire country to get one province. But that's not the whole point here.