I’m not sure you can make a STEAMpunk genere when steampunk already exists. And trying to make STEM into STEAM when it’s not a common acronym would cause a second layer of confusion. You’d be better off coming up with a new name. On top of that most of the “punk” generes follow a specific age that is driven by the name. Stream, Diesel, Atomic, Cyber, Solar, etc. STEM/STEAM is something that exists across many ages