Yes, suggestion of a pinnapple is great and that should be applied to bounties as well, and bounties could be claimed only by the guys within that 10 percent range.
However, there is a flaw in this idea?

And that is like KittyAustin, nobody is near her levels, so whom would she attack?
So many players in game may not have someone in their range, so what would they do, lols??

So, i again suggest that best idea is to limit the number of bounties per day, and that too, in the way that i suggested in the Official Announcements.
And second for low level players kicking high players 'coz they are cloaked, there is also a function in the game that stops someone from killing anybody in game more than 8 or 12 times per day. That should be reduced to even less like 4 or 5.