Do wonder how this will pan out. I have no interest in another monthly bill, however mini a cable bill it may be.
Apple should fix the App Store so developers can charge folks after major updates.
They do. It's called IAP.
For all my complaints about the App Store, there's not one of them.
Updates to apps should generally be free. If you've made a lot of new content (which I'd say is different from an "update"), then you can make it available as purchasable IAP/DLC/Expansion/whatever other name you want to call it.
Apple does need a way of offering demos...
I think the simplest solution would be to allow developers to mark some IAP as being the "standard" version of their app. In the app store, it would list the price of that IAP as being the price of the app, and an ordinary purchase of the app just includes that IAP. The App Store could have some icon to indicate "Demo Available" or something like that on such apps, and there can be some other button that customers can tap so that they instead download the free app without that IAP.
That would require very little from Apple... iOS and the apps themselves would be unchanged, developers would have a single optional metadata field of indicating which IAP is counted as "standard", and the store would need ~5 tiny changes, probably doable by a single developer in under a day, maybe another day or two to QA it (but it's Apple, so we know any QA is halfbaked at best and instead they'll let customers find the issue, then deploy another patch to the server a few days later.)