Well, the founder and president of Inti Creates was the director for Mega Man 7 and X2, but the entire company was made of ex-Capcom employees. Between them all, they probably worked on quite a bit more than that.
I used Mega Man X8 as an example, because it was the best Mega Man X game since X4, as well as the most recent one. The level designer for X8 was the same one from X4 as well. However, that level designer did not work on X5, X6, or X7. That's the crux of what I was talking about: there was no consistent team for any of the X series games. This "X games team" you yearned for to work on Mighty Number 9 doesn't exist. Capcom reshuffled staff for every game. If you look at the actual developer credits you can see that the staff changed quite a bit between entries.
Besides, the X series was really inconsistent in quality. X3 and X5 have some issues, but X6 had some pretty serious level design and collision issues, while X7 is a complete disaster that most of the fanbase tries to pretend was never made. The overall opinion of the fanbase on the Zero series is much better. I for one love the Zero series, and think they are the high-point of level design and physics in the franchise. Not that the ZX games were bad either. Moreover, Mega Man 9 is considered by many fans that I have seen online to be as good as Mega Man 2.