It almost sounds like the discussion of crewing the back of the Chinook has to go back to first principles; what effect do we want the crew in the back to achieve? Once that is decided then the crewing becomes pretty obvious.
From my perspective in the front the effect boils down to four key points:
1) The crew must be able to direct the aircraft, and provide the word picture to the front of what is going on, when trying to squeeze the aircraft into a confined area, with 10 foot rotor clearance, at night, with minimum illum. Unless all the crew members can do this they are dead-weight to me up front.
2) Must be able to defend the aircraft with whatever weapons systems are on board, if there is more than one type of weapon they must all be capable of operating it.
3) Must be able to load/unload, rig and/or hook a load, in as short a time as possible.
4) They must be able to conduct adequate maintenance and servicing while in flight or away from the Sqn. What constitutes this level of maintenance? I would say the highest level would be capable of pulling chip-detectors, determining whether it's real or fuzz and carrying on from there.
How do we accomplish this?
As I said in my first post, I think this can best be done through a mix of FE's and LM's. Again, I think we should be looking at a 3 man back seat crew, if this is 2 LM/1 FE or 1 LM/2 FE is immaterial, provided they can all achieve points 1 - 3 above.
Point 4 is going to be the domain of the FE's, but that doesn't absolve them from being just as proficient as LM's with the other 3 points. And it doesn't mean that LM's can not participate in point 4, there is no reason (at least no problem that can't be solved) a LM can not receive the same training and have the same understanding of aircraft systems as a pilot.
And to reiterate what others have said, if you are flying as crew then you are aircrew and subject to the same training requirements as everyone else, CAC/R2I, RUET, Av Med...etc. So no, now that we are out of the Afghan theatre, you can't just toss an Army guy in and call him a DG.
That's not to say I wouldn't want some Cbt Arms experience to tap into. Which is one of the reasons why I think separating LM from Traffic tech (at least on the Chinook) would be a good idea. I think over time we would attract Cbt Arms guys/gals to the community, bringing their experience with them; we would also attract other trades which would bring other skill sets and experience.
Cheers