I was also having ideas as I started to read this - initially leaning towards interaction with Moody-type ideas, FWIW - but the thought of Tonks and Luna and Thestrals has many intriguing possibilities, both serious (or Sirius, as shimotsuki has said!) and humorous. So my vote would be for that.

I've only recently had chance to start reading 'Raise Your Lantern High' again, and I will do some commenting, but it's proving a lovely way to start my day. (I get to read it at breakfast time!) And the work and thought you've put into it... Wow. :)