I was thinking of posting something along these lines, nice to see someone else also aware of this niche! Software point of view, you'd like to use QMK or ZMK,

I was thinking of posting something along these lines, nice to see someone else also aware of this niche! Software point of view, you'd like to use QMK or ZMK, and KiCad to design the hardware (PCBs). Reddit's r/olkb and r/ergomechkeyboards are great places to start! Bonus: QMK supports trackpads and nipple-pointers too! (Not sure about mice though)