Harmony - Troop Symmetry

In my humble opinion, a strict link to levels is not necessary. Nor is it necessary for elites/bases. In the case of Heroes of Might and Magic V, the most logical application of a level system is to determine the damage a hero inflicts on creatures with their non-magical attack.
To Nargott's credit, his mod does something similar. I remember that in the castles in WGE, levels are often duplicated.

Not quite. There will be a three- and four-tier building system, and at the same tier, different factions will have a different number of units (asymmetry). The tiers are formed based on the principle of equal strength or buyout price, but not on the principle of the same level. The number of levels remains the same – 7, and the difference between adjacent levels is approximately maintained at around 2 times the strength of a single creature.

I don't see the point in combining levels, as it reduces the diversity of stack sizes.