Snag being how th ehlicopter determines its height above landing area.......original post indicates an offset/circling approach where radalt data would not relate to landing area but only on approach.
Airfields where lower cat ILS are flown include all sorts of additional safeguards re protection and undershoot arcs etc.
Autoland to an airport - not such a huge problem, but autoland to an offset/90deg HLS...................pass the whiskey and big cigar co, and turn my baseball cap back to front whilst you're at it!!!