I may be looking at this at a different way but couldn't Ninja theory being weak in gameplay but strong in other area's be exactly why they chose them? They already know how to make the combat in DMC they wouldn't outsource if all they wanted to do was tweak the combat. Thus it seems to me Capcom was going for a true collaboration in so far as the developer they chose has weaknesses that are their strengths and vice versa. Which to me makes more sense then picking a dev company that's you're clone and has the same weaknesses.
When you say "they already know how to make combat" are you referring to Capcom or NT?
If you are referring to Capcom its NT that will develop the combat. If you are referring to NT most likely they cant compete with Capcom.
This is going to turn out as a completely different game if Capcom doesnt lay some hand in the development