It all made sense in this world, it followed "traditional" Westeros marriage ceremony and it made sense within these characters.

I would have been shocked if Ramsay didn't do what he did. If Ramsay decided to just wait until Sansa was ready would have been completely out of character for him. Plus Ramsay needs to put a baby in Sansa as quickly as possible to secure his place with his father, especially with his father about to have a potential baby boy.