Thank you @oeoeaio for this extensive investigation 
I dont feel very competent on the tech dimension of what you said, but there is something I don’t understand on the “features” and UX side, I would need some clarification 
What I understand is that proposing Stripe as a payment method would enable standing orders as a hub will be able to charge a customer the the basket at every OC, when the standing order repeats.
But for me the most important feature I had in mind with implementing a multi-vendor payment gateway, and that I think Stripe Connects does (but not the regular Stripe API keys) is saving a lot of work for the hub, who won’t have to collect the money from the customers and then pay the suppliers, the money flowing directly as “mapped” in the system (see my post on it here: How to offer Mangopay as a payment method to hubs? [Split Payments])
Is this feature included in Stripe Connect? I don’t read anything about it here so I’m not sure, sorry if I don’t understand everything
And that means also reworking some of the existing processes (like adding a step where the hub manager has to validate that the order has been delivered so that the money flows from the e-wallet of the customer to the e-wallets of the suppliers, hubs, and instance. I listed them in the other discussion, they apply to Mangopay or any multi-vendor payment gateway system).
If Stripe does that job in the way you plan to implement it, then it sounds like a more international option than Mangopay and would probably be a better value-for-work/money option for the whole community as it would benefit much more countries at once! We would probably need to propose Mangopay in France as well, but once the work has been done with Stripe, I guess it would be pretty similar with Mangopay later on. And we can start proposing Stripe to the hubs who can’t “collect and pay the suppliers” for legal reasons, so that would answer our need on a short term.