Check out this rather short article (with an interesting collection of photos, however) on doll designer Veik11, who has created several Lady Gaga Barbie dolls. I have to admit--I love the one with the hair bow. She's adorable.
Also... if a doll company came out with a Lady Gaga doll, I would buy one. In fact... I would even consider going in on a split for a Minimee head for Lady Gaga. I think she's a fascinating character. Hmm... I wonder if there is one in the works at Den of Angels yet?