It's very hard to know how things would turn out if they didn't have DFs. That means they would train in completely different ways. But if we were to remove someone's DF powers right on the spot, then Enel would be the obvious choice. He can still use his spear, but I don't think anyone would have much difficulty with him.Caribou would also be a very good choice.
I was going to say BB, but he was actually nominated for being a commander in WB's crew, so even without his DF, he still has very good base strength.
Smoker relies on his DF for some aerial combat, but his DF basically does nothing. All it does is let him smoke cigars without worrying about cancer :| But if you look at his fighting style, he uses a lot of physical attacks, so I think he'd be fine.
Another choice would be current Moriah. He relies completely on his DF. He would be a shell of himself if it was removed.