It is perfectly legal to use conductive sleeve/braid as the wire protection per <R7f>.
Such wire sleeve will let you electrically connect all parts of the robot and will help prevent static electricity built-up between them.
Once again, it is perfectly legal per <R7f> (See the Game Manual).
I understand that GDC ruled consistently with <R21> of “no modifications to electronic components”, but it is unfortunate that there is no detailed knowledge base article other that ESD Notice and it wasn’t linked from the Q&A.
A lot of teams are struggling with damaged hardware and VEX is mute on any hardware changes that could increase ESD protection.
Then if you really want to connect electrical V5 Brain ground to the robot chassis you can get creative with legacy wires and orange jumpers:
But you need to be very careful, because it could potentially create even more opportunities for ESD damage if metal subsystems of the robot are not electrically tied to the chassis first.