Does anyone else think that Tonks will be a bugger of a character to cast for the OOTP movie? You'd need more than one actress playing her if she is to feature in the film as much as in the book.
Nope. You just need one actress and a hell of a... of a... can't remember the word... the person-who-puts-make-up-on-actors. And there's digital technology, and all sorts of things. I don't think that many actresses playing one role would make a good effect.
I think make-up or digital trickery would just be an unnecessary expense. Warner Bros. will likely enough try to be as economic as possible and therefore just use different actresses. I agree that this particular method would probably not be done to good effect though.
Tonks changes her nose and hair the most often in the book. They could do that with one actress, wigs, and some great nose prosthetics done by a good makeup artist.