i was looking into this mod and it seems to be more ideal to use a dc to dc step down converter with 15-20 volts as 12 volts isnt required in the spec
found a nice write up for it here: https://github.com/LOLYsk/Gamecube-USB-C-PD-MOD

just a idea but would it be possible to make a new BBA using fpga hardware even though it would be impractical?
just something that crossed my mind and thought it was interesting