Make it 1:1 then a fair deal
Example:
People spend $1000 in ICO at $1 to get 1000 Token/Coins
People go now to Coinexchange to spent $1000 and get 33333 Coins
Now These People can swap those 33333 1:1 to new coin. This is fair to you?
But think about those people that sells it at lower price they lost too and the buyer gains. I think that's what trading/exchanges are for.