As a (soon-to-change) non-combatant, I've been assiduously reading the fora (yes, I did study Latin).
To me the argument about late-war Spits is not only about there not being a late-war Spit - the XIV - but also about late-war planes vs early or mid-war planes. It is manifestly unfair to put a 1939 plane against a 1942 plane, or a 1942 plane against a 1945 plane. While we all know that life and war are most definitely not fair, game balance demands some rectification.
I suggest that the rectification be to the scoring system. How about plus or minus 25% per year over 1 difference of mannufacture? Thus a ME262 (were it modelled) would score nothing for downing a Stuka, but a Stuka would score plenty for downing a ME 262.