Sid,
This topic comes up around every 7 years or so, I remember it at least three times during my military service.
First question: The line between Pilot & aircrewman? I'm not qualified to answer that question but my immediate thoughts are educational background, experience & training. (This is highly controversial and I don't say it to provoke a slanging match or a willy-waving competition).
Second question: Ask Sikorsky and the US military for their views. However, engine malfunction handling, tail stabilator emergencies and certain hydraulics failures all spring to mind. The operational role of the aircraft may require either pilot to handle the aircraft in critical situations, even approaches and hovering, but this is of course true of all larger helicopters. Covert NVG ops complicates this even further. This is a larger BATTLEFIELD aircraft we're talking about.
Third question: Rank is NOT an issue but see question 1. The two things are directly related. Generally speaking, you won't retain a well educated, highly trained and motivated individual if you give him low rank and low pay.
Another question from myself, it's been asked before but it is always relevant. Does the Army really have the engineering backup to fully support the BLUH concept in the field, especially in these times of strict downsizing and streamlining? Despite the undoubted increase in manning levels (?) due to the imminent arrival of the Apache, a larger aircraft requires more manpower than a smaller one. The usual theory "we'll just take over the redundant RAF engineers" doesn't hold any water.