We actually do have bosses that do things like aggro reset, or to ignore aggro for certain moves and just use them on whoever they want (or at least had, no idea if they were removed with the giant nerf-fest 3.1 was).

But honestly, most tanks can't even properly hold hate without any of these. If something like your ideas got implemented, it would have to be in hardcore raids with dedicated groups, not in content you do with random pugs.