So I added some sugar to that hive. It was in pretty bad nick, just about out of stores. There were a few more interesting things I noted though. The previous evening, around outside the hive were bees that had been out gathering pollen, but seem to have froze before getting back into the hive. These aren't old bees. Perfectly healthy bees which, being put into a sealed container and transported to warm room, would start buzzing around again like normal. The sun on the hive must have made them think it was warm enough and then a cool breeze, or something. Interesting because it was only evident with one hive.
On a more positive note, another more prosperous hive was given a quick inspection to give an idea of brood this time of year. They're storing honey in the migratory lid above their brood. God knows where they got it from, or how they managed to get out of the hive at all given the minimal amounts of sun and temperature. Interesting creatures, didn't expect that.
So that's my update. I still like this fondant idea.