From the tech trees of four campaigns, we can see that there are some rules the devs apply
(of course, there are exceptions:
- At the same level, both sides get the same class and same type of weapon.
- As players progress through the tech tree, they get weapons that have more firepower.
However, it is obvious that the developers are having a hard time filling out the tech tree. Sometimes one faction is given a good SMG while the other side is given a bad one. Or weapons whose existence are historically inaccurate are introduced.
I think developers are having a hard time with the tech tree because of one thing.
They are trying to make a symmetrical tech tree when the equipment of each faction is asymmetrical. Each faction have their own strengths and weaknesses(many people have mentioned this fact in the past). Developers should try to embrace more asymmetrical balance into the tech tree. Then the tech tree might be more historically accurate and interesting.