Well, after 40+ replies I guess I should sound off eh?
Very well,
Mine would be an RPG set in an FFXII esque universe, lots of airships but very little grit and grime, more high gloss and medieval esque symbolism. Basically Gaslamp Fantasy, not quite steampunk.
I would want the overall gameplay style to be what I hope Dragon Age will turn out to be. A party based RPG with Pause and Play combat, Mass Effect style Dialogue and Bethesda's knack for making every skill/ability at least somewhat useful in the overall game.
You would create the main character in the same sense that you "create" Cmdr. Shepard in Mass Effect, you decide on appearance, abilities and background, but the character has a personality, one that you can shape, but never truly define. As well the female Main Character would be voiced by Jennifer Hale. The male lead would be voiced by David Hayter, not doing his Snake voice, but he's wickedly compitent anyway.
Though it would have a WRPG feel overall, I'd like there to be some JRPG elements. Mainly the crazy enemys, elaborate but somewhat impractical weapons and the sometimes more colorful character designs. Basically it would end up looking similar to a more polished World of Warcraft when the product rolled out.
The music would be handled by Yasonori Mitsuda (Chrono Trigger).
The overall story planning would be handled by a combination of Drew Karpashyn (Biowares lead writer), Masati Kato (the Story man behind Chrono Trigger, Xenogears and Chrono Cross) and the original designer of Final Fantasy XII (he also did FF:Tactics and Vagrant Story but had a nervous breakdown while working on FFXII, he didn't end up finishing the game).
So, yeah, I'd want that game made for me.