[watahyahknow]

you could look around at wheelchair adaptations for cars , some of them allso have these sort of thing for when the person operating it doesnt have the strength or feet to operate the lever
from wat the picture of the system shows its nothing more than a linear servo , you could add one to under the dash mecanicly pressing the brakepedal lever above the footpad with a small roller , prolly can use a smaller less powerfull servo for that
retracted it doesnt mess up the pedal feel and extended it keeps all four wheels locked
it does put some force on the hydraulic lines and stuff but it would brake better than a emergenc brake does
i would still keep the original emergencybrake setup incase the hydraulics let go