The core issues with the Web Monetization API is that all the things you mentioned get dangerously close to SAP and Salesforce waters, and there's a reason these systems are the definition of bloated legacy accounting tech.
Our problem as a < 200 person non-profit is that our teams are being convinced that we _do_ need these systems, and in that scenario it is bloat. We keep telling ourselves that we need to "grow into" SalesForce and all its ancillaries that we're paying outrageous sums for. And that growth looks so much like a balloon. We have more and more SaaS stuff to support but the same number of people to do it. And we think we're getting ahead.