Have the phone boot into a "custom apps mode" where the only app you have is basic sms texting and phone (basically the minimum to call it a smartphone). Only allow custom apps to run in this mode.
People still have the 'freedom to do whatever they want with their own hardware', but they don't get to demand that Apple supports that freedom with the full iOS software.
This would be an excellent solution to the EU overreach.
Just a reminder to everybody supporting government overreach, while you're enjoying your third party apps the EU is making moves to destroy your privacy:
https://www.reddit.com/r/technology/comments/17rg58f/eu_article_45_requires_that_browsers_trust/