Hudson River Corridor is safe but challenging
I'll wade in as someone who occasionally flies this corridor. It's probably best avoided by inexperienced pilots, but my experience is that the helicopter pilots - including the Liberty Helicopter pilots - are extremely professional about making position reports and practicing see and avoid. You also have the option of flying a little higher and talking with Tower, and I've done that occasionally when traffic in the corridor is very busy.
I think that making the airspace positive control would simply put a strict limit on the amount of traffic that would be able to operate in this airspace. While that might make things a little safer, I don't believe the safety record in this airspace really requires that sort of approach. My personal feeling is leave the airspace alone, and continue to warn people to be alert and be careful out there.