1. This is not an alternative to a black list is it a form of a black list in that you are asking all miners to treat certain transactions differently than other transactions.
2. Your math is wrong. Let's say I am the owner of the black listed coins. All the miners have made an agreement to charge a 100% fee for transfers from the black listed addresses. I want to send 100 of my blacklisted coins. I enter a transaction for 100 coins from address A to address B. A 100% fee requirement would mean that I would need to pay 100 coins for the fee. A 200% fee requirement would mean I would need to add a 200 coin fee, etc. I get to keep and transfer the 100 coins, you have just made if very expensive for me to do the transfer.
3. You have made no changes to the protocol. You just have a "gentlemen's agreement" between all miners. Therefore a fee smaller than the 100% or 200% or whatever fee is still a valid transaction to all nodes. Therefore if even one miner decides to break ranks and mine a block with only a 50% fee on the black listed transactions it will be a validated transaction. If one miner takes the 50% fee there is nothing to prevent another miner from taking a 25% fee. And so it goes... All the other miners that still adhere to the agreement can chastise the miners that break the agreement but the fact is those that adhere to the agreement made
no money and those that break the agreement
make money.
So your statement
Miners would have all the interest to adhere to this update.
is not true.
