I have read this thread with great interest. As an ex-military pilot, instrument rating instructor and QHI with nearly 1000 hours 'actual' in helicopters, I think that a few important points have been missed here:
1. Instrument flying proficiency is a perishable skill. If not current, even the most talented and experienced pilot will struggle to accurately fly a helicopter on instruments manually.
2. Instrument flying currency affects capacity directly. I have seen (and been) a pilot who can manage to control the aircraft adequately in IMC, but struggle to communicate (or even speak in some cases) or make sensible decisions.
3. In my view, most helicopter accidents are not caused by lack of flying skill, but poor decision making. Giving a newbie a few hours on instruments in carefully controlled conditions may provide a confidence that is not warranted. I think that it would be a much better use of time and money to put the student in a suitable simulator, let him fly up a valley into IMC and see what happens. Then let him do it again and see if his decision changes.
By the way, for any FW pilot reading this thread, remember that unlike aeroplanes, helicopters are inherently unstable. This makes a huge difference in the effort required to control them (and not just in IMC).