You make it easy to add repositories which are on a whitelist that the distro maintains.
It's not damn rocket science. They want to add a repository, you check first to see if it's an allowed repository. Christ. That's my entire fucking point.
Pretty much any repository that had an actual real person or company behind it would be whitelisted.
Oh, that a nice, real-world solution: a central you-can - you-can't list. That's really going to work after 70% of the fashionable apps of the moment are still waiting in the debian repository approval queue. What about closed-source software? Will most distros include Adobe at the allowed list?.
And how are you going to prevent runnable Java applets (what the hell, even Firefox allows full-permission Java deployment these days) that will simply ask the user for the root password? Will you forbid running apps inside the user folder? Good luck with that, you just removed the Personal out of the PC. "What do you mean I can't run CuteBunnyGame? I'm going back to Windows, sorry."
You're still swimming in the failbucket, sorry.
Um, yes, there is. Namely, if they don't have to put in their root password for anything else, they just might get a little suspicious if they have to pull it out for malware.
I love the idea that people just do random things to operate their computer.
No, they are taught how to operate their computer. In Windows, they are taught to download and run, with admin permissions, the flash installer, or the Silverlight installer, or the Skype installer, or the malware installer, or RSS reader installer, or the...hey, wait, what was that one before the last one again?
If you don't teach them that's how you install programs, they don't install programs that way, and look askew at any programs that says they should be installed that way.
You seem to be the failbucket administrator. All of your ideas are complete consumer turn-offs. Teach them? Who is going to teach them? The product vendor, who needs the user for profit / religious reasons? Are you serious? I can even imagine the box: "Warning, this product is not suitable for idiot users like you who will insert their root passwords at any time asked. Please GTFO, RTFM and learn how to secure your computer before using this product".
People won't learn because they don't want to and most of the time they simply can't. And they don't give the root password to anyone because Windows taught them, they give it to anyone because they want to install CuteBunnyGame and CuteBunnyGame is asking for their password. They paid for their computer and they WANT to run CuteBunnyGame.
You zealots simply don't get normal people. That's why you're all swimming wildly inside the failbucket.
I swear, it's like no one here has any knowledge of how antivirus works at all, and is incapable of reading what I actually type. Malicious programs that run under a single user account are trivial to clean up, a hell of a lot easier to clean up than the rootkit infections that cripple Windows. You could even reboot the computer into an 'antivirus mode' where no user programs get executed at all. (You know, sorta like safe mode is supposed to work, except that none of the trojans on Windows are running under user accounts or via the normal startup, but have instead inserted themselves as system files.)
Who cares? The biggest issue is getting infected in the first place, not if it is easy or not to clean it up. If your personal files are gone (or someone is requesting ransom for them) or your computer is part of a botnet, you have bigger things to worry about than "trust the antivirus" or "just reinstall the damn thing". Even worse: most knowledgeable users would not trust an infected machine.