Placing a cost on individual miners means that there is an incentive to vote for no change, even if increasing the block size is a good idea. It is the standard free rider problem. If most miners vote yes, then it doesn't matter how you vote. If most vote No, then again it doesn't matter how you vote.
You could have the cost imposed on all miners once the change happens. If the block size increases by 10%, then the minting fee drops by 10%.
At one point, there was a suggestion to have a rule that the block size is limited by the tx fees. The more fees, the larger the block. A 2MB block would require fees of at least 50BTC (i.e. 2 * 25BTC). A 3MB block would require 75BTC in fees to be valid.
