Regular subsidies, reparations and even credits could be added in further updates!
Financial relationships would be great, aight?
Example 1: Your opponent obviously loses a city and you offer further peace in exchange for reparations — 5 stars per turn 5 turns.
Example 2: Your ally doesn't have a good time being at war with the common enemy. Thus, you decide to send 15 stars to boost your ally's military & economy.
Example 3: You really need to build expensive ports in a couple of turns and explore new continents, but you got no money. Ask your ally for 10 stars and return 2 stars 6 turns.
So, basically, Embassies will include this amazing ability (while Peace treaty will include reparations) instead of (or in addition to) mutual income, and you as a leader of a tribe will be able to set amount of stars you send or request.