1) if any dev want to avoid dumpers then they must limit bounty participants, the limit the participants they better ,if a bounty only request 300 participants at highest and the 300 became a dumper it won't hurt ,unlike 2000+ participants
2) devs should forget bounty when still on ICO ,allow bounties after your project finished ICO successfully and make your project is doing great before allowing bounty
This are just ideas ,if you have anything better please drop on here and let's share.
but it will not be fair to some people, especially to investors, they will feel it will not be good. i also don't really agree with this, because the price of tokens that we will get will probably be greater than eth or fiat that is given to us.