Mihawk's bounty being so high is anti-agenda, you use bounties=power cope you either lose the argument or you come up with dumb percentages like Shanks' 10% or BM is 20% stronger than Mihawk, this goes to shit the moment Zoro absolutely dominates Mihawk like he always does against his opponents, you use the Yonkou card, Mihawk can replace Buggy on a whim but he doesn't want to be a Yonkou, he prefers to have one as his personal janitor.
Mihawk would have an even higher bounty if he was the Yonkou and it can still grow, just wait for them to get something done.