> It's going to be a less secure system for casual users, but it'll allow power-users to more easily (you can do that on Android as well, but it's more difficult) secure their system as much as they want.
No, it really won't. Doing substantial privacy and security hardening requires a years of work by a team focused on it and the OS needs to be developed with it in mind. Sure, you can enable SELinux elsewhere, but you won't have anything remotely comparable to the complete, full system SELinux policies developed as part of the Android Open Source Project and deeply integrated into it. You're talking about users doing all this from scratch somehow when there is hardly any interest in it for that ecosystem. There's barely any application sandbox or permission model to speak of and projects like Flatpak are not approaching it in a meaningful way that avoids trusting apps.
You're suggesting throwing out having an application security model and all this privacy / security work to reinvent it all from scratch for a new ecosystem without existing applications. It's hard to understand how that makes anything easier.
Having the well-defined base OS with verified boot and clear separation between the OS and applications which are sandboxed and offered capabilities via a permission model is crucial. It's not an advantage for security to completely do away with that. It's important to implement each feature / capability in a way that fits into the overall security model. Developers love taking shortcuts and doing this in a lazy / negligent way, and you can see exactly that with how people implement features via the shortest path of depending on app-accessible root instead of doing it properly, even when that's a niche thing.
