User blog comment:Pandawarrior/What if Luffy and the SHs had joined the Whitebeard Pirates?/@comment-3435506-20111201002501/@comment-3181121-20111201002813

The war would have definitely been delayed, if not completely cancelled, as Ace would have shown Luffy and the gang where to find Whitebeard. Teach captured Ace to gain the Shichibukai title, if Ace had been with whitebeard he wouldn't have been captured. Teach would have gone for somebody else. Also, while he might not have necessarily learned the gears, the commanders are capable of Haki, and might have shown it to him.