I would say give these boys two things: (1) Oxygen bottles for the first month, and (3) give back their old long-barreled FN's in 7.62 NATO. That way, if they spot some Taliban 400 yards away, they have a prayer of (a) hitting the SOB and (b) killing same.
Also, how about blood doping? There are only a few of them after all.
The old Bootnecks are tough bas***ds, and don't need too many of them, to make there presence known. I used the British version of the FN FAL, we called it the SLR 7.62, phased out for the SA-80 5.56mm. However, I much prefer the M-16, but theres only one weapon i'd give all of those for and thats the GPMG (Gimpy) 7.62 HMG, I love that weapon. The M-16 is a better rifle than the SA-80, and the boys from the Mountain and arctic warfare cadre use the M-16, as well as the Commando battalions Recce troops. The SA-80s only effective as an individual weapon up to 300 metres, 600 metres if used as a section support weapon. But its big Brother, the LSW is good up to 800 metres, but thats nothing compared to my baby, the Gimpys 1100-1800 metres.
Don't know about the oxygen bottles, I would have thought the mountain troops were acclimatised (the Mountain and arctic warfare cadre definately are) to the heights. One things for definate though, 'don't f**k with the Royal Marine Commandos'. I had a Training Corporal at ITC Catterick last year, who had passed the all-arms commando course at the Royal Marines Lympstone, He'd go out on runs with his dog, and by the time he'd finished running, the dog needed to be carried.