Not sure it'd mix too well... MGS tried hard to make things "seem" real. FF tries hard to make things unreal yet believable, within the context of the game anyway. I can't imagine a FF set in modern-day earthian society. If you want that, take Earthbound and make it... serious? Not sure that's possible lol...

I loved the industiral slums of FF7 and steam-punk of FF6. I think it'd be nice to have a psuedo-post-apocolyptic setting. So maybe Fallout? Or Phantasy Star... something. I dunno