As stated earlier by someone else, I wouldn't mind Elaine as a helping character for Guybrush to get, I dunno, an item or something.
An example that comes to mind is Majora's Mask with the Kafei mission where the player plays as both Link and Kafei to get to the other side (sounds like a chicken joke... digressing) so with that as an example, I wouldn't mind playing around as Elaine alongside Guybrush. Heck, I wouldn't mind temporarily playing as Elaine to get Guybrush out of a cage or something (again, with the Kafei mission in mind).
I don't care, I said 40 hours. It's gonna be 40 hours. Player Be Damned!
-Ron Gilbert, MI2:SE Commentary