Probably QMK, since that's the only firmware i know even a little. I'm still pretty new to mechanical keyboards and i've only had one ever.
I figure i'll cut it out of paper or cardboard to make sure the keys aren't positioned way off from where they should be and i can reach most of it from the home row, then i'll probably go straight to having a circuit board printed. I'll look into getting help with that part since i haven't made a circuit board before and don't know the process for going from a picture in Inkscape to a printable file.
Shame about the half size switches. I suppose i could just use the regular function keys on my laptop's built in keyboard and move some symbols from the number pad to other keys. The other modifications to fit more full keys aren't too bad.

