Of the planes on the list, I'd have to vote for the P-39 first. There are so many variants and types, and it was used widely enough for me to be curious about it.
If HT does add the P-39, PLEASE add both early and late-war models (D/N/Q), and take a look at the british variant (P-400) with the hispano as well. The P-63 would be nice, but would take additional modeling time since it is slightly larger airframe than the original P-39.
2nd Vote goes to the G.55, because we need more Axis rides, and the G.55 would be interesting to try out against the C.205 and the 109G2/G6.
3rd Vote goes to the A-26, because it would make a great perk bomber and I haven't got anything to spend bomber perks on.
EagleDNY
$.02
-- voting machine lever pulled.