For me, a big first step would be making all factions able to fight early infantry engagements on a equal footing.
They can. Base infantry in early engagements is equal.
Micro should be the decisive factor to win first battles.
It is.
Having factions with starting units that clearly are superior to others changes the game to a cat & mouse chase since the first minute, which is not really fun, specially for the player with the worst unit.
Cons are actually superior to others as starter units.
That is not really an allied issue only, but I think that axis early game is much more flexible and adaptable. USF only has rifles and Soviets are locked in their choosed tier.
Axis are the locked factions. Sov can lateralise with callins. You have it backwards.