Placing NFOs in the H-60 was looked at for similar reasons. It was rejected because it was determined that the second pilot in a helo was needed for safety. The onstation flying was determined to be more "manual" and "fatiguing" then that of the S-3 and therefore required a copilot able to periodically relieve the pilot.
This was looked at again recently.
The onstation flying, especially with the MAD out can be quite demanding. However, since only the ATO (left-seater) has the MPD and computer keyset, often there is no real good way to swap pilots when it gets busy in an ASW or multiple threat ASST problem.
The big problem I see with having NFO's in the HSL community would be getting new guys deck qual'ed and current. You would have to kick out the NFO to get it done, unless they wanted to go to a TACAIR style qualification scheme.
Also, the whole H2P/HAC thing would have to be overhauled.
Don't get me wrong, when I was getting my ATO quals I was wishing for an NFO. However, it would require such a paradigm shift in the community, that unless it came from on high, it's not going to happen.