I find the Seafire to be, by far, the hardest carrier aircraft to land on a carrier in AH. The A6Ms, F4Fs, F4Us and F6F are all vastly easier. Being designed from the ground up as a carrier aircraft has distinct advantages.
Keep in mind that the British never would have done the Seafire if the Royal Navy had been able to procure aircraft, but the RAF completely controlled aircraft procurement and the RN was only able to beg for the scraps of what the RAF had decided to order. The Seafire was the best thing they could get under those circumstances, unless they wanted to keep on going with Skuas and Rocs or rely on the uncertain availability of the Martlet (F4F).
That being the case, I really don't see a need for the USN to navalize P-51s when they already have the superb F6F and F4U.