I am thinking among the same lines myself.
CONTESTET TERRITORIES
I figure the attacker should have 3 options. After the first round he can press attack, stay or retreat. Just as in the real war, it should be your choice if you want to continue the attack until the territory is conquered, or you want to stop the battle but stay in the territory to contest it, or just retreat. Remember that a territory is large as a country, and a turn is 3 months, and there was no phase during the real WWII where Germany or Russia vacated Poland with a small force, just to trade it back and forth, like we usually see in A&A games.
THE BATTLEBOARD
The 1914 Battleboard is perfect for WWII. G40 infantry should att at 2 and def at 3, because a 1940 infantry division had a lot more firepower than the 1914 infantry counterpart. And the 1940 tank should absorb two hits, because the maneuver warfare tactic was to break through the enemy line at the weak point, and then cut off the enemy supply, and this made few casualties but big surrenders. On the other hand, the classic assault with artillery barrage and infantry charges was a meat grinder with lots of casualties, and no surrender. So yes, artillery hit on 4 or less, they are the King of the battlefield, and tank hit on 2 but can absorb 2 hits.
DOGFIGHT
Yes, you must fight for air superiority before the ground battle. I think fighters should cost 6 or 8, and att 1 and def 2, both in air combat and later in ground strafing. This will be historically correct. Then the Stuka can hit ground units on a 3, or on a 4 if combined with a tank. And the bomber should carpet bombard huge infantry stacks, maybe like the classic AA gun, roll one dice for each inf, every 1 a hit. I also believe that an airbase should be able to scramble 3 fighters to an adjacent territory under attack, and not just seazones.
AMPHIBIOUS ASSAULTS
I love the 1914 rule that give the defending artillery a preemptive roll against amphibious assaulting ground units. This is exactly how it was on Dday and every other landing during both WWs. Maybe even the inf should attack on 1 in the first round of a landing, since the tanks don’t absorb hits when wading ashore. Then we can have Marines that still attack on 2 during landings