Okay then, any outfit aside from the vault suit should give negatives until your character has worn them for a week or so, and, depending on the outfit, maybe the doctor's scrubs could give you a small 5% bonus after another week of wear.
Hmm.. I think my idea was probably influenced by Rogue Galaxy. I hadn't realized that till just now.
I like my idea better though.. I always liked the looks of the metal armor much better than power armor and resented having to wear it.

If I like the looks of an outfit then I think it should be possible to improve the effectiveness of it to where it is as good as power armor or even better.
I liked the way each character in PS: Torment had their own style of armor, but I think more depth could have gone into that. It would have been far more interesting if each character's outfit (and weapons) could have been upgraded several times, rather than simply tossing out the old one for a better one.
Edit:
Brother None said:
Hey, if it means less Fallout 3 fans going to NMA and DaC and going to Planet Fallout instead, I'm a-ok with that.
So in your opinion what would a Fallout 3 fan be?
A. Someone who is like, "Fallout 3 is going to be THE BEST! game ever! It's great! Woooo!"
or
B. Someone who plans on buying Fallout 3 but hasn't yet decided whether they are going to like it or not.
orrrr..
C. B, except the decide they like Fallout 3 after purchasing it.