Doflamingo is a very powerful fighter but Luffy has certainly surpassed him at this point. His string abilities just won’t be enough to break through Luffy’s haki or deal enough meaningful damage to put him down. At this point Luffy is in a completely different league and wouldn’t need any gears to win this. A few haki infused punches would be enough to take Doflamingo down for the count. Luffy wins.