I am waiting since Day 1 for a campaign like this. I really enjoyed campaigns like Frostgrave, Dust Zverograd, Necromunda or Nuclear Renaissance.
Campaigns are highly addictive but the advantages you gain from expanding shouldn't be gamebreaking. You could do it income based. Starting with a 750$ Posse. Then you have farmland region worth 50$, a town with a railway station worth 80$ or a 100$ casino.
You could add territories. Like there is a 100$ casino, 50$ farmland and 10$ well inside a territory. If you control all three points of interest inside said territory you gain 1 additional influence for your posse. (There is still influence in the 2nd edition right?)