I'm with JWA - The crumple zone in the E-series will not do anything in most crashes. High-speed into a stationary object, maybe. Into another car, no.
I hit a metal freeway barrier with my van at 60 MPH, only the left radius arm bracket bent. Frame did not need straightening from this.
This Ambulance was in a 50 MPH head-on crash with a Chevy Tahoe, and it looks like the frame on this is still fine too.
But... I can understand any reservations a TUV officer may have, since a front hitch would stiffen it even more. The rear pair of bolts really don't do much, except resist negative tongue-weight forces, which are unlikely on a front hitch. You could easily replace these with a shear-bolt, and maintain full functionality of the hitch. In a crash, once the shear bolts shear, the hitch would no longer bridge the crumple-zone.