So then, let me ask you. Why isn't Mihawk a Yonko? We are told in the manga, that Kaido became a Yonko based on his strength alone, and he's worth 4.6 billion.
We already see that the WG doesn't give you a choice in the matter. They dub who they believe should be a Yonko, and that's the final word. So one can't say it's because Mihawk doesn't want to be.
The math ain't adding up here, if Kaido, strength wise is only worth about 2 billion, yet his strength, and only his strength is what allowed him to become a Yonko, yet Mihawk, who is worth 4 billion strength wise, wasn't instantly called a Yonko once the schichibukai was dissolved...
So if we are following this train of thought, then Kaido is worth over 4 billion strength wise, due to that being the determining factor of a single individual becoming a Yonko based on strength,because Mihawk isn't one at 3.6, but Kaido became one based on strength and is sitting at 4.6.