I don’t know many (any) Warre beekeepers who requeen their hives as a practice. However, I have requeened very hot Warre hives using a method he describes in his book. Essentially you take a queen excluder, place it over an empty box or two, put boxes full of brood comb (and we assume the queen) on top of the excluder. Smoke downward. Pull off the boxes and the queen should be scrambling to get through the excluder. It’s a pretty quick process that doesn’t require much searching – in fact, it’s probably quicker than finding an unmarked queen in many Langstroth hives!
I’ve had mice in my hives, but not while there were empty boxes. I only had mice move into the Warres because I forgot to get mouse guards on them in the fall. In the spring/summer/early fall the colony is generally strong enough to protect their hive from mice.
If by nuc you mean smaller Warre boxes (5 frame), we don’t sell them, and I don’t know anyone who does. I don’t see a reason to make them rather than just using the already small boxes as they are. No need to complicate things with multiple box sizes!