Though... you know, I would LOVE to allow the minor races to expand like major races. Everyone says I can't do that but I could you know. Please guys? Like, maybe an option to allow the minors to grow?
I thought the premise was you against the SK. If the minor races grow, then it is no longer 1on1, with minors being a resource to exploit. They will compete for city placement, etc.
If you do decide to let them grow, I think it should be in line with the story. That is:
1) If they align with SK - they should follow his directives and NOT grow. SK has his own expansions. (SK could force the minor to provide some troop support to those cities, though).
2) If they align with you, they gain confidence to defy the SK and will expand, and SK will of course target them as well (take some pressure off). But they should not expand until after you ally with them. This would also provide another consideration to whether or when you want to ally with minors. If this is the case, there should be an option in dialogs with the minors that would provide 0 influence change, not just +/-.