SASless, LHX initial competition included some single pilot proposals. IMO, the problem with the Army taking the risk to go to single pilot has to do with mission / task loading. (See old arguments about the old single pilot A-7 being a 1.3 pilot aircraft with 1.0 pilots ... )
At the time of the Comanche program, besides the attack and scout community being wedded to dual pilot models, there was considerable risk involved in how much task loading the fancy electronic side of the development was going to be able to handle, particularly as the "Force XXI" vision made the Comanche an integral part of the CC and sensor mix, above and beyond scout and armed attack. I wish I could still get in touch with a few people I knew on that program to elaborate, but it's been a few years.
If you constrain the mission to "scout" or "armed scout" and take advantage of the current tools that allow for mission tasks to be assisted, I think you can make a good argument for a single pilot scout helicopter. You will need to change your training scheme a bit, however.
Getting the "system" to believe that you can do that is another matter, which has to do with human engineering.
EDIT: I found it!
http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf
See pages 17 and 18 of the report, dated 1986, regarding the risks for single pilot LHX. Lots of very interesting and prescient points raised in the paper.