Ooh. I like that. A fresh take on the Ars Magica troupe play. Each teacher has their "teacher's pet" a la Dumbledore/Harry; Snape//Malfoy; Sprout/Neville*; MacGonagall/Hermione.
Ii wouldn't want everyone to play a house elf. Partly because, in canon, they are very limited in what they are allowed to do because, you know, the slavery. But maybe players could choose between one of magical peoples. Elves, goblins, centaurs, giants, werewolves, etc.
But I have made no plans for this as yet. It is only a distant possible eventuality. I mean... now I'm thinking about it. Thanks. Like I don't have enough half-formed campaign ideas taking up space in my head. To make room for this one I'm going to have to forget something else, like how to drive.
*I'm not sure about this one. Neville is Gryffindor, surely Sprout would pick someone from Hufflepuff.