What middleman do you want to cut out? My proposal doesn't add any dependencies. It's also not possible to prevent duplicate charges if a user POSTs a form twic

What middleman do you want to cut out? My proposal doesn't add any dependencies. It's also not possible to prevent duplicate charges if a user POSTs a form twice without idempotency keys, so idempotency is necessary. I'm really not sure what you're actually proposing?