Elite Bodyguard - the type you describe - has notably been used
here which was probably the only setup that attempted to be balanced that I saw. It's also been used in troll/random setups or setups designed to be
ultra swingy, but meh. It's a rare role - especially so in the last three or so years - and there are some more in older setups, but I got bored so etc.
I think it's a very strong role that would be difficult to balance for - unlike Vig, Vengeful, Supersaint or other Town killing roles I can think of, Elite Bodyguard's got very little net loss for poor role usage and very high net gain for appropriate role usage. The issue with super potent hero roles like that is that balance swings heavily on their survival/appropriate usage and counter-roles, which are chaotic and relatively unpredictable variables. I'm pretty comfortable saying that variation of BG should never become Normal, but it may still have a place in a wackier setup somewhere.
My first Normal setup was pretty swingy; this one was an attempt to make something a little more even whilst still having its own ~quirk~.
