I think only one test bed p-51 was ever "navalized" so it wouldn't make much sense to do work on that model seeing as how only one was made and it never progressed any further. I guess for a "what if" plane it might be cool but I could think of a lot of more interesting planes Id love to see done first.
What you said is very true. In this new patch, if you were to use the WAW mod, and scroll to the '1946_GB_USA' section (Almost to the end of the plane list), you will see the FO-2 (P-38T), a navalized P-38, which never made it pass the drawing stage. Hence, this suggestion of mine.
With that said, there are lots of planes that the warring nations developed (pre-WW2, WW2, Cold War), with some being prototypes, while others are drawings. Let's see what the developers can come out with.
Nevertheless, it just keeps getting better and making such a classic game enjoyable