Are you asking for opinions?
Because in my opinion, I don't think you need the specials in order for it to be "complete".
To me they are extras.
For the ultimate completed book, then yes, you do need the special cards in order to get the special characters.
I wasn't sure what you were asking here, so if you meant something else, please clarify.
No, they aren't necessary for the game to be "complete" but if you want the special charecters there is space for them even after completing all of the normal villagers. So really it's personal preference as Rainey said.