Is growth scale must in a long game?

[Truper]

Immigration - either from someone else's provinces or from nowhere - would be nice, but it never actually happens.

Not so. I've had it happen - once.

The message read that a huge number of people had immigrated to the province. It was not a very populous province to start with, and it was hard to tell how many a "huge number" was. I'm guessing 25%.