Most of the time there's more than enough admins/ ONLY ONEmod on anyway.
Ok Seriously. I think this is a good suggestion, but I also have my doubts about it. As CJ said, watching ppl for cbug/switch/cheats is admins job. Also when there are no admins/mods online there is the Cheater reports section on the forum.
As for to just spying on people, it really sounds fun, and is a great way to be afk (if they don't disconnect) or just watching, and helping eachother out. But also, it could be abused (as an advanced /locate).
But if it were accepted, I think it should let people know they're being watched by donators or something. Like when someone's duelling, you can watch them from their angle, to see their aiming etc.. but It should give them a warning message..