I am planning to make this mac & cheese and want to know if I can assemble all ingredients together and wait until the following day to bake and serve without compromising the integrity of the dish.
I would consider baking it now and reheating the next day.
When making mac and cheese, I often assemble it and then bake it the following day. In my view it dries out when reheated.
If it MUST be prepared ahead I would go with SKK's approach. In the middle of the night you might perhaps think of other things you can work into it; lobster, mushrooms, whatever. BUT there is no way that your pasta is not going to dry out with an overnight rest. That's the trade off.