Just as a suggestion - I think you're throwing away tons and tons of possible flavour, in looking for too much consistency.
Think faction styles here, military structures, etc. For example's sake I'll make up a fictional faction, the "Koontzian Meritocracy" with forward-thinking and progressive ideals. These guys have a very different troop structure, because they believe in lots of upward mobility. So the lowliest Koontzian unit can, eventually, be upgraded to the highest one. It'll just take a long time. What's more, they have a verbose and florid manner of speech, so their unit names are distinctive and idiosyncratic, from Procrator to Warden of Serenity Vale (an honorary title with regards to a long-ago battle), to Knight of the Garter. Whereas their foes, the Lazarene Oligarchs, have a very rigid class structure and a formal, crisp diction. So no unit ever upgrades more than two steps beyond where it started, unit names are drab and descriptive, and the progression is always "____ Tertius", "____ Secundus", "_____ Prime".
There's huge amounts of possible style here; you made a start on that with the original concept for the mod, and I'm suggesting you go further in that direction, rather than further in the other. Increases replay value, too, as you're curious to find out how it'll play out with the very different troop trees - not just unit stats, but the tree's very structure.
"A foolish consistency is the hobgoblin of little minds." - Emerson