Testing the shift from historical-inspired to fantasy inspired, I'd say -
- for me, I overhauled it by the mods mentioned below: fixing pikes, the lost confederate ability - (which the AI wouldn't use but the player could - was looking into that ); raiding from camps - and the Ostros.
I was shown a list of all the bugs someone had fixed- between that and realizing the other team was surely out-modding me; I hung up modding ATW.

If I were to play again, I'd probably use the Hunnic mod I mentioned; been forever so I've forgotten their project & name - but if they ever finished it, can't be too many other modders whose research has been published ( mine on quora doesn't count I think :) so shouldn't be too hard to track down.
I heard someone had finally modded my oldest pet peeve - linking recruits to population & class -
but I'm not sure which TW they addressed.
Those two are on my to-play list next time TW bug bites me , which I think is the answer of what overhauls I'll use next time.

So what overhaul do you use then? Attila tests many new mechanics, ai and features. It was left unfinished like most TW games, but I like to find good overhaul mods that fix its problems.

tldr: yes, that's vanilla- I replaced the pike formations with other troops in personal mods , and that made it into my Ostro mod- not sure if that went into the Tribal Confederations mod or not, BUT the point before I rambled was; while I don't think the AI uses them well enough for most to notice unless the human is playing them; still...
Easily replaced by levy-tier infantry as you like.

(sorry for the formatting ) - it's vanilla, I tried to answer where I modded it out; and tried to recall the mod team that was pursuing similar historical research and ideas.

That said, if such interests you, in my mod research I found out another modder had much the same conclusion(s) - but years head start and a team - and his research became published!
I don't recall the team/ mod offhand, but if any of my niggles are your own, i'd look there-
from my PoV, Attila was mostly to test the horde mechanics with a game they already had, in preparation for the unannounced game they were working on - which was warhammer tw- so if their take on attila is a bit chaos horde - well...

hi, lilshep- that's in VANILLA, not mod.

( I did mod that out- sources imply they fought with spear/shieldwall tactics- which in previous era the Romans called "phalanx" - but extending that to mean the later pike phalanxes, is I believe incorrect. - also, pike use requires a bit of training and discipline, above even that required for a reliable wall- so hardly "levy" quality; but i digress. It was modded in my Ostrogoth mod- the people later called that were, at the time period, part of Attila's confederation forces - that mod got some work, but neither ever really finished ).
...Attila removing that the "horde" was ( as all empires are ) masses of assimilated/confederated people - was one of the choices ( like the seals ) that made me lose interest - so the migrators using such an advanced formation became the least of my niggles.

What is the submod?