I believe puppets in the game are underpowered. To make them more useful, I propose the following buffs:
Defensive Support: When invaded, puppets should defend their parent nation and provide a small amount of economic aid.
Resource Allocation Slider: Players should be able to adjust the amount of resources (up to 30%) and troops (up to 10%) that puppets contribute.
Puppet Loyalty: The likelihood of a puppet revolting should depend on how heavily they are exploited. Overly exploitative actions increase the risk of rebellion.