Ironically it might be the last iPhone I use, even though I believe very much in free-as-in-speech software on my devices.

This just bludgeons so much of the security model of the iPhone. I get that this is by Apple's design, in that conflating the security model of the iPhone with App Store lock-in has been a gold mine, but I just don't see how you provide the same malware guarantees without that enforcement.

EDIT: Not sure why the downvotes, I guess it's from people that are big free-software-at-any-cost advocates. The cost of doing this is going to be too high for most iPhone users - I very much doubt this is in their best interests overall.