I’ve built a SaaS website with subscriptions, enabled by an external payments processor (which could be Stripe, Braintree, Paddle, etc.).
Now this website for my SaaS ha
I think the mobile banking applications is simple example one of them. You can pay your bills, send money via mobile banking apps. But there is no need to use Google Play Service for billing. The all transactions will complete on the banking side. You can even send money directly to some betting sites. (If you want I'll share with some mobile banking apps for this features but you need to login, you have to be customer of the app owner bank)
I just want to share it for an idea, I think you can build your own crypto currency with Ethereum infrastructure called smart contracts. Its really easy to deploy. You can find 10mins tutorials for this. You can use as a money in your mobile app. In this way If someone need to be buy something they have to be purchase some of your crypto currency. And the google side you will be exception because of this,
"Payment is for digital content that may be consumed outside of the app itself (e.g. songs that can be played on other music players)"
But as you said,
it’s entirely up to Google’s discretion whether using an external payments processor is allowed or not, based on one’s interpretation of the terms presented above.
I'll signing under this.
You can also examine crypto stock market applications. I can bet they did not charge Google Play commission
Some of the information is not exactly what you want, but it's just for sharing ideas.