If the bounty can use ETH as a payment method, then I believe that the bounty activity can attract more professional hunters, but sadly most merchants will not accept such an idea!
You must really be delusional. There's really so such thing as professional hunters. Just hunters who know how to get the most out of bounties, 100% for their benefit and 0% for their projects. Paying in ETH will probably attract the more serious people true, but it will also attract the scammers with their hundreds of multi accounts.
I would agree that campaigns paying in hard crypto like ETH/BTC should be the way for serious projects to go, but this must also come with strict implementation of the campaign. A good manager that monitors QUALITY, not just ACTIVITY. A campaign that has objectives, not just numbers. Members that are active participants in crypto, not just bounty hunters.