I can't help but wonder if Apple would allow developers to follow the letter of the law, but attempt to circumvent the revenue drain via UI. Which is to say: Provide subscription options through both web and iOS APIs, but specifically advise users that signing up through iOS is damaging to the survival of the service, and strongly encouraging them to use a user-friendly UIWebView to sign up instead. Perhaps even non-monetary rewards could be attached to avoiding the iOS signup process (badges, points, etc.)
Not that I put it past Apple to reject it anyway. Just wondering how far that line could be pushed.
11.14 -- Apps that link to external mechanisms for purchasing content to be used in the app, such as a “buy" button that goes to a web site to purchase a digital book, will be rejected
I'd say it's safe to assume they'd reject you for even asking users to sign up through Safari, instead.
Not that I put it past Apple to reject it anyway. Just wondering how far that line could be pushed.