How long can the existing Puma airframes last, though?
Which would it make more sense to retire - ageing Pumas or near-new Merlins (the latter sharing considerable commonality with Navy Merlins, some engine commonality with the AH, etc.)?
Facing the decision of which do you buy more of, Pumas or Merlins - the right answer must be Merlin - though it should be a Merlin like the Italian Mk 413, navalised with folding tailboom and rotors. Then the Sea King 4 could perhaps be taken out of service and its logistics chain removed.
And if there really is a need for a smaller platform, then augment the Chinooks and Merlins with AW139 or NH90.
I'm not anti-Puma by any means - I have stick time in the Puma, and I spent some very, very happy times with 33 and 1563 Flight and have a real soft spot for the old girl, and for the blokes who operate it. I'm aware of some of the extraordinary missions and roles that have been flown by the Puma in Iraq, and of the kit used, and I am profoundly sad (but accepting of the fact) that the likes of me can't write about them - the Puma boys deserve great credit for what they've achieved. I'm surprised that you haven't laboured the advantage of the big doors on BOTH sides.
The Wessex was a great aircraft, too, but that does not mean that it should still be in use, nor that we should be buying a new production Super Wessex were it still in production.