I think another challenge with this approach would be marketing/awareness. With app updates, current users are notified that there is a new version. If you pu

I think another challenge with this approach would be marketing/awareness. With app updates, current users are notified that there is a new version. If you put out a new version separate from the previous one then your existing user base is unaware that there is a new (and better?) version of XYZ app. It's just messy. Paid upgrades directly supported by the App Store/OS would be much better IMO.