Dynamic subscription payments with Braintree API?

Hi, I’m building a bubble application in which company’s pay yearly subscription plans according to the amount of employees they have. My plan is to give company’s the ability to add “employee capacity” easily by increasing their yearly payment depending on how many more employees they want to provide access to. After some research it seems like Braintree is the best option for this, but it seems like I would have to use their API rather than just the braintree plugin. They don’t have REST API so I don’t see how I could use the Bubble API connector. Any ideas how I might implement this payment scheme on my application?