Then, that hodler will have a choice: sign those coins, and send them as fees, or not sign those coins, and effectively get them excluded from the circulation.
Leaving out the specifics of how much you would take, if you want to go down this route then you would need to create some kind of automatic mechanism to take these coins from people, and not rely on them spending them as enforced fees, as there would be an incentive for individuals to let these coins be excluded from the circulation as it would make their other coins more scarce and therefore more valuable.
Then look again at Paul Sztorc's triangle, and choose wisely: Merged Mining or big blocks? And if something else, then what it would be?
So, given that the majority of bitcoin blocks are already taking part in one or more merged mining protocols, what are the main arguments against using merged mining to create security once the block subsidy is insufficient? Is there any ongoing discussion or work on blind merged mining protocols (such as BIP 301)?