The simplest solution I have seen, that has a precedent (most other A&A games were this way) and makes a marked/strong change in game; without adding units or changing setup is this:
Adjust the turn order to Russia, Germany, Japan etc.
This temporal shift gives HUGE weight exactly where it’s needed by the allies, and deletes the single most back breaking weapon in the axis arsenal - the Italian can opener on the eastern front. Further - Russia is badly in need of reinforcement; and this temporal shift means it’s a “build” ahead of the axis. Exactly the right allotment that’s needed; and it’s not placed on the board prior to setup.
Further; the imbalanced NO’s like 5 for every city and caucusus in Russia, are now appropriate more challenging to achieve; and significant to recieve; instead of the all but guaranteed waltz in.
On the flip side - Late game - the axis can use the G/J can opener; and it can be deadly if played right; but atleast Russia has been in the fight this long; and it’s choices with it’s eastern most forces can deter this outcome.