Would it be possible to use less stylized (not with the Doc's devices) character generation menus, for an alternate start mod, like those in FO3? Or were the old ones replaced and can no longer be used?

Not sure what you mean, the character creation menus are all pretty much identical to those in FO3. There actually is a remnant of a different trait menu in the game, but it's /more/ "stylized" if anything (ShowTraitMenu is the one in use, ShowTraitSelectMenu gives you a medical form to fill out)

I'm actually working on a mod to get a MORE stylized character generation, but it's all in-game. You can probably edit the XML for skill and trait menus, but the race/face/hair menu(s) are hard-coded. You can easily make them not pop up, but you can't 'tweak' them: you'd have to replace them entirely (Which is probably never going to happen for facegen configuration and apparently almost as hard for hair and eyes. FOSE never had the functions, the only person to ever do it wrote a custom FOSE plugin)

Edit: Oh, just remembered the Vigor-Tester. I guess you could call that stylized, though no more than the SPECIAL book really. The world model for the book is still in-game, but I don't know about the menu (I doubt it). You probably don't want your gritty cowboy selecting attributes from a children's book anyway. Attributes are trivial to set, however. Dunno if you can create a whole new menu like the skills/trait menus though, since mod-configuration items I've seen have always been very poor it's possible there are limitations. Or people are just lazy.