Think you are still missing the point:
1) Any faction can used as the benchmark
2) If that faction is wins more game vs other you buff the other faction
3) If that faction loses more games vs other you nerf the other faction
Finally the just because a faction is balanced it does not mean that some of components can not be up or op if it part of the design of the faction. And this is how ostheer were designed. Less cost efficient infatry more cost efficient support weapon. Weaker light vehicles more powerful medium tanks.
Again it does not matter what you use as your benchmark as long at it stay the same.
What I actually tried to explain is that using a faction as benchmark is the wrong approach. It multiplies workload, cannot account for non-comparable units and also hardly for skill gaps.
I agree with your second part, ehich also feeds into my point about benchmark factions: it does not work very well. If a faction is supposed to have certain power spikes. How do you balance for that since you cannot directly compare unit stats to make them roughly equal? What do we do if MGs work well against mid and close range squads but get frontally wiped by a single long range squad while all long range squads are roughly similarly strong? Benchmarking this would find no issue at all, since similar units perform similarly.
That's why I said that you need to balance according to their available counters. Of course you can balance and compare to similar units, but for this you assume that the other unit is decently balanced and that you can take this unit's performance out of faction context.