While adding my ideas on a forum topic I realized the tiltle as Shichibukai my be the best position in the OP world. I say that because no matter how you look at it the pros largely outweigh the cons. The only cons that I see is that in the very unlikely chance the WG faces someone on Yonko level you will have to assist them in the battle. And Shichibukai pay a tax to the WG. Besides that as long as you do not do anything stupid like try to take over a WG protected county(and get caught) or attack a World Noble you probably could get away with anything(like selling humans for example). And when it comes down to it in the case where you have to fight in a battle against Yonkou level adversaries is that the Marines are helping you clear the way to One Piece. All of the shichibukai that seem like they are interested in OP were having fun during the war(Doflamingo, Crocodile, Teach, Moria) at least to some extent.
To all those thinking that the Pirate King is obviously the best position, it would be much easier reaching OP without opposition from the WG and Marines. As far as being the owner of OP and a Shichibukai I don't think its possible, but for those who don't have that ambition(maybe Mihawk, Jinbei, Handcock) Shichibukai may be the next best thing.