I've decided to change my steamwork fester to a steamwork endeavor, and I've got the items ready. However, I can't remember if I have to use some random endeavor elixir on her first or if I can just turn in the endeavor schematics and she'll be rebuilt into one. I thought I read once that you can do the latter, but I could be getting that confused with being able to build a pet from scratch. :x
(I don't want to give her up and build a new one though, even if it'd be cheaper and she'd have a special gear gender. I've invested too much time and sp in her stats.)
My Steamwork Tutani was a Nightmare Jollin until he got his change from the Schematic so I'd assume the same would happen if you switch from one SW species to another.