I personally don't like this idea because bounty hunting is not common and people only use hitman mode to not get arrested by cops. And people don't bounty other people that often anymore from my observation or when people do, its only 2k. I would not say bounty hunting is OP in any way.
I agree with whats being said here but reading this gave me another idea... Small feature, but what if the bounty placer is able to set a timer in which his bounty is to be claimed...?