This might just make mining those altcoins unprofitable altogether. And how do you solve the available market volume issue?
nah, it is actually interesting because it is cutting the extra step that altcoin miners have to take by charging them a fee. basically altcoin miners are mining altcoins then have to wait they receive the coin and move it to an exchange to dump and them cash out the bitcoins.
OP is just cutting those middle steps and gives them bitcoin although it seems like the fee he is charging is huge though.
When you exchange Altcoin to BTC you pay way more than 2% if you account for exchange conversion and withdrawal fees plus network transaction fees.
Just a BTC transaction can cost anywhere between 1 to 5 USD. Exchanges charge 0.25% + withdrawal fees that are usually a fixed amount. Add up all of these fees and you'll get way more than 2% of the amount you're withdrawing from pools.