Unfortunately the way he describes the "Ulysses Pact" is fantasy. He makes it sound like it would be just like today, except a savvy user could sideload Signal for example if Apple was compelled to remove it. What would _actually_ happen is a long list of companies would say "brilliant, we don't have to conform to the app store guidelines any more" and go sideload-exclusive. Within a matter of months it would be common for users to have both official and unofficial app stores, sowing widespread confusion, and UX would go to pot while apps run in the background, chew up battery and take advantage of undocumented/buggy APIs to track users or steal data.
The warlord analogy is a good one. It's a tough nut to crack. The only defensive mechanism that's actionable for the average user is to keep as much data as possible offline. Sure, if Apple wants to they can ship code that exfiltrates data off my external USB hard drive, but that's way beyond the threat model we're discussing today.