I think they have a few guys that could do well in the UFC. Guys like ERic Kelly, Roy Docyogen, Bae Young Kwon, Bibiano Fernandes, Eduard Folayang, Masakatsu Ueda, Shinya Aoki would all have good success in the UFC. Boku, Soo Chul Kim would all do okay.
IMO Soo Chul Kim has a TON of potential. He is really, really improving and only 21 years old right now. He is a strong kid as well and I think he would do better vs most American wrestlers then many of the other Japanese imports.
I really think that kid has a bright future. Could be the best Japanese fighter in the world in 5 years.
Also I agree with you there are a couple guys that I think could work there way up to 10 fighters in the UFC. I don't see anyone right now that I think could challenge for a title but I see guys that could be above the middle tier for sure.