Separately, Kato also worked on FFVII, FFXI, Baten Kaitos, and he is doing Children of Mana and Seiken Densetsu 4. Mitsuda worked on FFV, Secret of Mana, Romancing SaGa 2, Front Mission, Mario Party, Xenosaga Episode I and probably other stuff.
Mitsuda did Mario Party 2 (a little), Bomberman 64, and Shadow Hearts 1 and 2 as well.
Kato didn't work on any FFs. If he did, I haven't seen him in any of the credits of any of them and I can't find him in any of them online.
Xenogears is amazing...but not that great. It's story and music are good, but everything else?
...it's incomplete. If they don't consider it incomplete, then it's poorly made. There's a reason Tetsuya Takahashi is "redoing" the Xeno games, not creating the prequels to Xenogears.
EDIT: Well, unless Wikipedia is making things up, apparently Chrono is right. Kato did work on FF7 and FFXI. 7 is understandable...but what the hell would he do with FFXI? He was probably in the office for five minutes.