I missed the poll...
We must think what are the planesets that need more models, and most representative models, not only the planes we would like to fly around in...
So far, the US and UK planesets are quite complete... The British planeset could use a EW/MW bomber, maybe the Wellington. The german planeset IMHO only needs one aircraft to reach the same level: the He-111.
The major problems are in the Japanese planeset - now a little Bettyer - the Russian and the Italian planesets...
The Russian planeset needs desperately of a fighter, a medium bomber and maybe - I say maybe - a heavy bomber (maybe not).
The Italian planeset needs desperately of, at least, one medium bomber and maybe, maybe, another fighter.
But the greatest HOLE in AH planeset id the French... It's a pity that we do not have the D520, and one French medium and one heavy bomber represented.
I would go for the He-111 first, then move to the Russian planeset. Then to the French and the Italian one on each turn until all basic models were in here...
But I lost the poll...