Right, working on every device requires a hardware solution. I haven’t encountered any such hardware yet but I do know that it is possible. Next, your second requirement makes what you’re trying to accomplish impossible. Privilege escalation by definition will escalate the privilege. The problem lies in the fact that the root user is basically a god in linux. You can even wipe your system if you so desire. However, you can read more into SELinux or other similar systems. It works by basically running check on the kernel level not user level. But the only solutions I can think of will make other day-to-day tasks more of a hassle. Also, note that whoever knows how to modify the SELinux can also bypass the system. I found an answer on serverfault that points to a blog. However, I haven’t read the blog yet. You may find an answer there.