I have this idea for a Harry Potter sequel series. Sometime after the ending of the eighth film (when everyone is now adults), a orphan muggle boy who live off the streets of London stumbled upon an magical relict. The mysterious item gets infused into his skin, granting him wizard powers. The wizarding world took an interest in him. When he turn 11, he is accepted to Hogwarts; the first muggle to ever to be accepted. Harry Potter can play a minor role in this, and his kids can go to school with the muggle boy. I've already come up with a name for him: "Jeremy Marx".

I'm just saying if that ever happens, I have a great idea who would in it.
Malcolm McDowell or Jared Harris - the headmaster of the school.
Benedict Cumberbatch - the Defense Against the Dark Art teacher (which will be stay throughout the series this time).
Stephen Merchant - a teacher for Muggle Studies.