Dont tell me Buggy is a D too?
But strange, Buggy wants to be a Pirate King but he doesn't want One Piece. He's after Captain's John treasure.
WB wants a family and I have no idea what Shanks want.
Should the WG ever try to make it there and bury the truth once and for all, keeping Buggy close could be a massive trump card ( assuming he knows how to get there ).
That or they want Buggy's Pirate at their side. Buggy ain't powerful yet but his crews are lvl 3-5 of Impel Down. Together they are easily shicibukai lvl