I think you will find that ANY ship built in the UK, for a UK company, using government loans, MUST be built to conform to Government specs to be able to convert that ship to be suitable for government use during time of war. QE2 was no exception.
Plans exist for the conversion of the QE2 to an Armed Merchant Cruiser if war is declared. Obviously these plans were not used during the Falklands because of time constraints. During the Falklands they put a heli deck on the front without strengthening because the strength was already there to take a 6' gun. Back end same thing using the swimming pools that were empty.
As for the helicopter deck it was capable of taking the largest helicopters in use at the time of design. Equivalent of a Wessex.
Interesting story here. QE 2 had a helicopter deck....so they decided to send 2 people to school to use the paddles to guide the helo's in. BUT, the first time a helo landed, both theses people were on vacation so one of the Masters at Arms volunteered to do the job.....the helo came out and the MAA started...the bridge got a frantic message from the pilot..."Get that idiot of my landing site!"
Interesting about the Trafalgar pics...the helo landed backwards.