Aoki would win a couple of fights, but he'd lose many more than he'd win.
The LW divison has a lot of wrestlers who have improved striking, and Aoki would get murdered by these guys. No wrestler is going to slam Aoki to the ground when he can use his wrestling to keep it standing and pick him apart on the feet.
He'd get killed be Penn, it would be worse than Sanchez, based on his terrible striking and his inability to take Penn down (there's no way in hell that happens, I'd bet my life on it).
Florian, Sanchez, etc, would also keep it standing and take him out on the feet.
Basically, there's far too many good, solid wrestlers (or people who have good TDD and other clinch skills), who have good enough striking to pick him apart, as well as guys like Sanchez, Florian, Penn, that beat him in every aspect except BJJ, and they can all keep it standing.
He's not a bad fighter, in fact, his BJJ is amazing, he's very solid at it and I'd love to see him on the ground with Penn, but his lack of wrestling and serious lack of striking would make it hard for him to get to the top of the UFC LW division.