Aoki has never really performed well outside of Japan. His only win outside of his home country was against Lyle Beerbohm, a guy who is pretty much a can in my eyes. Aoki's resume is mostly padded with cans with a few mid-level fighters sprinkled here and there.
He may be able to make an impact at 145 but I doubt he'll ever dominate the UFC. Without the special rules matches, the rainbow pants, and the Japanese judging/reffing bias he won't be able to do much.