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.
Again it does not matter if their are power spikes in faction by design. If one use the grenadier as benchmark one might choose to say that other infatry should be 15% more cost efficient than grenadier since grenadier are support by 15% more cost efficient support weapons.
Trying to balance this with a faction can be equally problematic since unit might be equally balanced but other factor have a major impact like tech cost and timing.
My point is simply if all mainlines infantries are buffed then one is not solving the balance issue on the same power level but one is creating a power creep.