May you suggest you focus super hard on customer support? The support I’ve gotten from mobile finance (Simple, Chime, Revolut, Acorns) has been at best underwhelming. I’ve mostly stopped using these kinds of services because I don’t trust them to handle things well if I ever have a problem.
Everything. Slow email support. Different customer service rep every iteration. Replacing debit card. Debugging declined transactions with sufficient money. All of it.
Good luck! It looks like a super cool idea.