Chicorbeef has been advocating for totally removing the CS bonus. I'm coming around to this way of thinking as wel, but with a caveat: What if the Khan was buffed more?
I really liked Mongolia in Vanilla because they were a civ that had a pitiful UA, but whose UUs were so good that it compensated. Their Medieval power spike was so large that the civ felt like it was designed to have that carry them through the rest of the game. In VP, Mongolia is one of 2 civs with a UU that gives persistent bonuses across all eras (the other being Assyria), and the only one that never expires. Leveraging that to put more weight on the Khan, and less on the UA sounds like a great way to differentiate Mongolia.
So, remove the bonus to heavy tribute from UA
Ideas for Khan boosts (pick 1 or 2):
- Stacked unit gains "Keshik" promotion: +25% defense, +1 attack
- Every Khan on Empire makes makes intimidating City States easier - increases 'Overall Military Power' for intimidating city states calculation by 50%
- Units starting stacked or adjacent to a Khan gain 1 move this turn (an inverse of the SapMovementAura effect)