Well, in a 1943 setup, particularly if you start it after Kursk which would be about mid-July, the Allies would have almost overwhelming numerical superiority. Perhaps to balance it out you would give the Axis certain techs like Jet Fighters, Rockets, perhaps Super Subs and maybe even Improved Mechanized Infantry. See if the Axis can hold out with slightly better equipment versus a hoard of Allied units.
By the way, I think Italy was pretty much out of the game by July 1943, although you could probably put German units in Northern Italy.
Me and a friend tried something out way back with Classic. Axis units were really strong, Infantry hitting @ 2 on attack, Tanks @ 4, Fighters @ 4, Subs @ 3 and gave them Heavy Bombers. However, their stuff was expensive, like 150% of normal cost.
Meanwhile the Allies stuff was relatively weak. Infantry @ 1 attack and defense, Tanks @ 2, etc. I think all units attack/defense factors were down by 1 (unless they were already @ 1. Everything would at least get an attack or defense value of 1). However, their stuff was really cheap. I think 75% of normal cost, with a couple possibly less.
Basically, we wanted to see which would win between strong and expensive units and weak and cheap units.
The cheap units won the day. Even with their great hitting power, the Axis just couldn’t plow through large numbers of cheap units. They made a lot of advancements right at first but in just a couple of rounds the Allies had huge numbers and even with weak hit numbers, when you have enough units to roll for you will eventually get hits and the Axis units were so expensive that they had relatively few units anywhere.
Just an interesting little test.