Do you have any suggestions?
I think making the colonization system a bit closer to Victoria's would be a very good move.
Instead of having to send zillions of colonists it would be better to have "claims" to uncolonized province, like it happened historically. To get these claims you could do number of things, like build trade posts, forts, missions and so on. (once the province is cleared of hostile natives)
Then we would need some kind of emigration system to allow for the mainland's pop to move to the colonies, something like a new slider...one side would improve the colony's pop at the cost of mainland pop and vice versa.