As a concept artist, I can tell you that, even in the little shitty game were making, a concept artist doesn't really get away with all he wants, nor is the work you see on the media really his own. I go trough constant hoops all day to get even one little thing to look like I did it. All of my concepts get so scrutinized by committee that by the time the thing has been filtered trough enough eyes, I can barely recognize it.
So, just cause Nomura puts shit on paper doesn't mean that its magically in the game SPECIALLY on such a huge company like SE were everything is under watch by a million eyes. Is it his fault that Lightning and Cloud look similar? Of course not, thats a decision made by a team of people who feel that its a much better use of resources to re-use the same model. Smart move too. Video Games are always publicized to make believe 3 people make them and that is probably the biggest misunderstanding of all.
You can say that Nomura's style is all belts and girly hair, but honestly, the guy just follows current fashion standards in Japan, and that is a smart move to make (and obviously successful) In Final Fantasy games hes the concept artist, true, but not the ART DIRECTOR. Remember, thats who the Concept guy bows to, thats the guy who decides how faces are shaped, if the guys wear belts or not, of they all look like girls or whatever. Then once the AD decides on a look, he presents it to the Producer and Director who will review it, then they themselves show the art to the Executive Producers and Marketing and THEY review it as well. At any spot they can send it back and ask for a do-over or just start the whole process from scratch.
Art wise, Nomura will do his thing and not have a very varied facial style, but the same happens to MANY Japanese and American artists. Its the higher ups at SE that have the final call and make him the poster boy for FF design, hes pretty extravagant after all and not a bad choice really.
Hell if anything Id go on a limb and say that Nomuras style is versatile! Look at his FF VII art, then look at his Kingdom Hearts art, then his FF X art. He also did a lot of texture work on Advent Children and that movie is gorgeous if nothing else. Its not just all characters you know, hell its not that easy. What the public sees is just about 5 percent of the work a Concept Artist puts in a game.
This KH 2 piece he did for example
Now hey, SE doesn't really show that since its not very marketable to the general public that buys the game, but thats a VERY valuable concept piece to have in production, and I'm sure if the guy has moved up in SE so much is because he brings invaluable contributions to the way the games look (after all, the characters are only what, 10 percent of the whole game?)
Sorry about the rant, just felt like I could bring in something relevant :)