CAD (cardboard aided design) is really powerful. You get to fail fast: figuring out things don’t work before more expensive manufacturing steps (such as laser cutting).
And using inkscape is fine, but even better if you print it out and stick it to cardboard.
I started with a Hakko, $120. It blows my mind how much better a $25 soldering iron (Pinecil V2) is. Both only have 2 buttons, but the Hakko does a terrible job with them. The Hakko also takes significantly longer to heat, which resulted in me running it really hot when I first started out.
My hope was that I would sub a 3 finger control to a 1 finger control, opening up the other two for other things - but thinking about it more now leads me to believe that fingers just wouldn’t bend that way.
I think you might be right. It might make sense for me to repurpose an existing design.