Doflamingo and his crew alone could probably do nothing, but Dofla is the center king pin of all the Criminal underworld, all the brokers
if you think of Luffy, Law and their crews fighting alone of course they'd lose
but if you addthe Kid, Killer, Apoo, and Hawkings alliance
Doflamingo and his entire crew
plus the entire criminal underworld which seems to have people like CP9, Gecko Moria (at least he looks that way to me) and tons of other brokers we've only seen silhouettes of
and Big Mom is part of the underworldmy guess is that's his play, If doflamingo is forced to fight with the entire underworld by his side, Big Mom might join in the battle with the odds in her favor of defeating Kaidou with all these new allies
and then Law's plan will get shot to shit when she opens that treasure box and that Bomb goes off
then they go from, having the entire underworld and another Yonkou at there side = Sure win
To, Having two Yonkou that utterly despise them = extremely fuckedand then of course Oda would do his magic and I won't even attempt to think that far ahead in Oda's brain
I'm not really convinced that Law's big move is to use Doflamingo to force various Brokers to team up and fight Kaido. Based on what he says to Doflamino when they're initially negotiating and on his actions at Green Bit, he seemed to be hoping for the Navy to interfere in the situation and, unless Law is confident he can take down an admiral, I don't see how he would expect Doflamingo to be free to direct his crew and various other brokers to fall in step with Law and Luffy. It's true that Law has stated that dealing with a Yonkou with a small number of people is impossible, but bolstering his forces in that manner seems like a really absurd plan. And not to mention, if Big Mam has brokers, chances are that Kaidou has a few as well and all it takes is one leak and Kaidou's aware of what's coming for him.