I think as an aspirational thing balance by sides is good to strive for, but I don’t know how you’d really make that determination until the exact changes are set in stone and you can run a large enough sample of test games, or hold a couple tournaments to tally the wins.
Instead I’d suggest that the impression of fairness, and the entertainment value, comes about when players feel like there are multiple viable routes to victory for either side, and not just one or two scripted openings you have to follow for one side or the other to have a chance of winning. In that respect you can basically substitute newness for balance, because it takes a while for players to learn the new systems and get used to them.
This mod at least addresses a few of the normal complaints with the boxed game, namely that America is too cash strapped and slow on the uptakes, that China is too weak, that France is rather boring and irrelevant after the opening round, that it’s hard (particularly for the Allies) to develop enough transport capacity to be effective against bombers, and that the Russian NOs feel too difficult to achieve.
There are several HR proposals that have been made for global, but absent a popular mod that organizes them together and makes them easy to implement and test, it’s hard to get enough traction and bring the player base behind them. If this mod gains in popularity and more people decide to try it, I’d say that’s probably a good thing, whatever the ultimate determination about balance by sides ends up being.
My only other suggestion, beyond the Sierra Leone thing, is not to make too many updates too quickly, or be too quick to accept annectodatal or passionate initial reactions as a reason to make significant or sweeping alterations in rapid succession, before people have a chance to really sink their teeth into it. This can derail the progress of the mod into a state of perpetual alpha testing. If it produces entertaining gameplay and satisfies the basic desire to have multiple viable paths to victory, then you can always address the balance by sides later, with the introduction of a new NO, or the elimination of an NO, or simply by changing the value of an existing NO. Tweaking the objective money is fairly simple (compared to a rule change say). But its hard to see which side might need the tweak until the core mod has been played more or less to death for a year haha