Besides some of the ideas already mentioned....

I'd like a late 1800s/early 1900s Jewish Immigrant doll... they could do 1894 for it.

I'd like more non-doll books, like History Mysteries were.

I'd like more books like the AG character Mysteries set after the main 6 books.

I'd like Girls of Many Lands to continue, if not with dolls, than at least books. I'd like Italy, Spain, Russia, Japan... so many ideas, maybe one from South America?