Thank you Yarkis for your insights. I believe some of these issues might be the result of the fact that we hardly get to play campaigns since we are too busy modding...
I've only started a new campaign now and, like you, I don't feel the need for Provincial Line, since I don't have enough money to support so many stacks that I would reach my Line Infantry unit limit. Unit limits is something that can be addressed easily. Unit balancing will be another matter - as I said before this is a grey zone for me, so I'll leave that to Sage
Maybe it's also an opportunity to revise the unit rosters on a per-faction basis. Also, I've been putting new regions into the startpos file - we're just not using them yet because we wanted to ensure compatibility with people's ongoing campaigns. But with those changes it should be possible, for example, to make a unit available only
outside a nation's home regions.
Anyway, you've given us some food for thought