I have done this and all my saves have the lots from my library that I need. My library is my final save. I can recreate any storyline by choosing lots from my library and dropping them into the worlds. My favorite households are saved in my library as well. I try not to re-download them into new saves because I prefer the households to keep friends and family connections. I play the same save with new lots and fresh worlds in order to have multiple saves and still keep my households and friendships undisturbed (connected). 🙂
I am waiting for major fixes in For Rent and City Living before I can fully play my game. Dine Out works but it's not fixed.