I think the Seafire III should be added since it was far more common than our Seafire IIc and the III entered service in Nov 43, putting it in mid-late war arenas.
However, it should be the last aircraft added after all the others are added, namely an Axis transport and bomber.
Even changing our current Seafire IIc to the more common L IIc would go a long way.
Our current IIc seems to be a sort of cross between an early Vb provided by the RAF to the Navy/FAA, but with 120 rounds of cannon as in later ones.
Most produced II was the L IIc, the small batch of early IIc's were very quickly re-engined to Merlin 32's and also became L IIc's.
So what they had -
IIc - Very small number of initial Seafires with Merlin 45/46 (quickly re-engined to L IIc specs)
L IIc - Lions share of the 400 odd Seafires II's produced.
L III - Most produced wartime Seafire, over 1200.
There were also a handfull of Seafire F III's fitted with cameras and re-designated FR III's.
Although I've not played for a while, every scenario that I played in would have had the historically used L III if available, but had to sub the L IIc.