>then the private key of this digital signature is a "god object"

You could instead require the app to be part of the OS. The next gotcha would from you I imagine is that the build farm for the next OS update is a god object and at that point I think this is a meaningless tangent. I'll concede and say you have to trust your OS creator. But you always have to trust your OS creator for any OS.

>then you basically have passwordless sudo

If sudo couldn't be used from other programs / she'll scripts and doesn't give access to a god account, but instead did simple things like let you use ping, then that seems fine to me. But why require people to manually wrap programs when it could be handled automatically.

>Either way, there is some source of authority in here

Sure, but it's a system that's much better than sudo.

> the build farm for the next OS update is a god object

This is a very interesting question! It may sound meaningless to you, but modifying firmware images is pretty common when trying to modify locked-down hardware. As in, "I'll unpack the firmware image, set root password and enable telnet, then flash it back". So no, the build farm is not a god object. Whatever controls firmware updates is. Can any app initiate it? Or does it need user's password? Or maybe physical presence? Or a private key that only select people have?

> If sudo couldn't be used from other programs / she'll scripts and doesn't give access to a god account.. But why require people to manually wrap programs..

So, you mean like what "polkit"? This is what systemd is doing - instead of requiring "sudo", commands like "systemctl start SOMETHING" will handle privilege escalation themselves. For example on my computer, running this in terminal pops-up interactive dialog asking for my password. In theory, you can have the whole suite of programs - "secure-cp", "secure-mv", "secure-edit" (see also: "sudoedit"), "secure-find", etc... But it seems pretty wasteful, no? Sure, most common actions (installing/removing apps, configuring networks) can get its own nice privilege-escalating wrappers, but there are many advanced tasks that user can do, and it's much easier to make (and audit) a single "sudo" than hundreds of random scripts.

(Unless you want to have a fully locked-down system where the only OS creator can decide which privileged actions are allowed. Those things exists and are pretty popular: Android and iOS. They are also only usable for a very specific purposes, basically as a remote terminals to server machines running unrestricted OSes without such limitations)

> You could instead require the app to be part of the OS.

That almost sounds like you're advocating for the abolishment of third party or user-made apps that can make changes to the system without the approval of the manufacturer.