You definitely need a safety feature such as the spring system. Two reasons...
Prevent/minimise damage to the car it's mounted on.
Prevent/minimise damage to other venicles or objects AND people who get hit by it.
If on a kit car I suspect it would fail passing at the inspection phase for edges/projections too "sharp" plus rigidity. Maybe even issues at MOT ( or equivalent outside UK) and a modification for insurance. Non standard part post homoligation.
