As a 500 hr plus Merlin driver I think there is a lot of common sense being written here (which makes a chnage when you get into the Merlin SH debate).
There is no doubt that the aircraft is a good CSAR platform with plenty of legs and capacity. Aditionally the Mk3 has probably got the only wire cutters of all UK aircraft types (correct me if I am wrong, please).
It is not a heavy lifter and was never claimed to be so but it outdoes the Sea King. Theire are only 2 true heavy lifters in the world and they are streaks ahead of the rest - CH47 and CH53.
Keeping aside from the US presidential debate the Merlin or US101 has a real chance of getting the USAF CSAR role which is up for grabs.
As for affording it, the aircraft is already fitted with a FLIR (which admitedly could be better) and reasonable DAS (the same as Apache).
I don't think we can always rely on the Yanks to rescue our guys especially when George W decides its got nothing to with him.