@Darth:
Eh, not really.
First of all, they will still have Kuma.
Mihawk doesn't care.
Boa has been more of a hindrance than help.
Doflamingo as well.
And so was Law.
Buggy is rather useless.
And let's be honest here, if the pirate want's to stay a pirate, he needs to fight other pirates.
How much could Doflamingo do, if the WG didn't protect him?
The problem with Shichibukai is that they can't be forced to act by the pure threats, because Doflamingo himself states that he can quit any time he wants. We know that it's not true, but he can still act like it is. That institution, as it is presented right now, is completly useless.
And also, why would Shichibukai fight against goverment directly? Even Yonkou aren't that stupid.
You've made some very good points about the Shicibukai . They're often working against the government covertly, and they often benefit from the reputation and sway their status gives them. It's arguable that they've been more of a liability than a boon so far, and they're very tempramental
But you're not giving them any credit for what they bring to the table. They are required to answer to the world government. They can't work against the world government (actively and openly at least). Then there's their reputation. As far as the world knows, right now the WG has the following individuals batting for them
The infamous pirate empress, scourge of men
The strongest swordsman in the world
A vicious pirate nicknamed tyrant, and mindless WG slave. Kuma
A bloodthirsty young pirate, part of the worst generation, with a ridiculous former bounty. law
The cruel, psychotic, feared spawn of the world nobles. doflamingo
and most useful/frightening of all
The pirate king's crewmate. Shanks's brother in arms. The man who teamed up with whitebeard during the war. Co-instigator of the impel down prison break. Leader of a fiercely loyal band of impel down escapees. Good pal of strawhat luffy. A man who is incredibly rich, and managed to keep a low profile for decades. Buggy
all they need to do is wreck a few small timers, clash with a few yonkou captains and the WG's cache grows
and like I said, the WG needs more suordinates and less enemies. not the other way around