@marktuff Anytime!
So, what I do in my app is they start with a free trial. After their free trial they need to enter a credit card and choose a plan, which is just their subscription to use my platform.
Should they choose to register as a seller, they just go through the simple Stripe Express process and they are set.
My sellers, all have individual ‘portals’ that their users can browse and purchase things from. All I do here is charge that users card, and direct payment to the seller. (In which case I believe the built in bubble one will do just fine, as in your question/example.)
I think I’ll need to do more testing, as I’m unsure to be honest, and certainly not a Stripe expert. 
On the other hand, I’ve seen posts by @keith that explain iterating through a list. (Keith, sorry to bother you with a tag, but I figured you may have some cool insight on iterating through a cart to shed light in this example) So in your case of having a ‘cart’, you’d iterate through that list and grab the carts items ‘stripe_user_id’ and either run the charge method, or transfer method as I showed up above using their ID.
Reading through what Levon mentioned, I think he and I are thinking somewhat the same thing, and will probably render the same result.
*Edit: I found it. I think with this cool little plugin, it may be of help: