Agreed. Furthermore, I'd say that MA functionality is no longer an issue. The best heavy bomber of the war is represented. The best jet of the war is represented. The best medium bombers and dive bombers are represented. The best piston driven fighters (with differences of opinion) are represented. The best tanks (again, with differences of opinion) are represented. Ship-wise, for the most part, the best is already represented, as well.
About the only thing left to be modeled there would be based on missing functionality (DD torps, etc.).
So, I contend that the only real reason left to add a plane, vehicle or even a ship would be to fill gaps for events. I agree with Perdue that the King Cobra would naturally fall to the bottom of such a list (as would the Meteor, unless the V-1 is modeled for some odd reason and such an event would be player vs AI).
What we're facing, unfortunately, is a drop in event participation driving a lack of motivation to add:
Fiat G.50 (Battle of Britain, North Africa and Med, Finland)
IAR 80/IAR 81 (Romania, Eastern Front - Battle of Stalingrad, Ploiesti)
Kawasaki Ki-100 (Defense of Japan - B-29 raids)
Mikoyan-Gurevich MiG-3 (Eastern Front)
Mitsubishi J2M (Battle of Philippine Sea, Home Defense - B-29 raids)
Bristol Type 156 Beaufighter (France, Norway, Belgium, Pacific, Burma)
Petlyakov Pe-3 (Eastern Front)
Handley Page Halifax (Used heavily in the Euro Campaign)
Short Stirling (earlier bombing campaign Euro)
Armstrong Whitworth Whitley (Bombing campaign Euro, special duties)
Bristol Beaufort (Euro, Pacific, Burma, Malaya)
Dornier Do 217 (West and South Europe)
Savoia-Marchetti SM.79 (Italy's most prolific bomber/torpedo bomber)
Curtiss SB2C Helldiver (Mid-war to late-war carrier based USN dive bomber)
Douglas TBD Devastator (USN early war torpedo bomber)
Nakajima B6N (IJN mid/late war torpedo bomber)
Then there might be consideration for the Ju-52 as well as perhaps modeling gliders for D-Day. If FPS was ever to be a practicality in AH then the Armstrong Whitworth Whitney shuttling commandos might become quite popular.
Players on the forum can argue the merits of such a list to their heart's content and I may offer pros and cons each way but any plane added from the above list would be great, imo.
But, if there's nobody participating in events I'm not sure HT and co. would see it worth their time.