It'll be a nightmare to get an in-app change like this through their approval process. OP's solution to offload the entire thing to the web is a great stop-gap measure since when it is definitely rejected they can appeal through their App Store rep pointing to this external payment URL decision and have some small chance of getting it approved in the nearest term.
If you pay for something in the app apple gets 30% of that money. If you send users to your website to pay you get to keep it all now that the 27% fee was found illegal.
I don't know about iOS, but on Android you can just pay through a Google Pay pop-up, you don't need to input any kind of payment information to the app itself. Does iOS not have such a mechanism?
iOS does and of course you can call an in-app Safari popup to any payment processor or website (with limitations on JavaScript speed) if you don't want to pop them into a browser and then back into the app.
- Why not just handle all of this in the app? Do you think Apple won't allow it?
- Are you geofencing this functionality? It seems like per other comments this is US only.
- How are you handling existing subscribers (not sure if applicable)? Will you "encourage" them to migrate?