It is very easy, now that we are observing the results of Russia's BTG system in Ukraine to find all sorts of ways to talk it down.
For reminder: a Russian BTG is 550-750 soldiers, and comprises organic AA, artillery, infantry and armor.
However, until right before 2022 Ukraine war, the consensus was, IIRC, quite different. Russia had re-organized from its Georgia experience and was up for business with tightly integrated, flexible, land combined arms units. Most press coverage I recall, up to 2022, was quite positive (and worried, if Western).
Now, with hindsight, I myself can see one big advantage from BTG: ease of coordinating different unit types, which was always perceived to be a Russian weakness. But also 2 disadvantages:
the multiple weapon systems - AA, artillery, logistics, AFV - all require specialized technical and maintenance personnel. On the scale of 550-750 people that risks getting a lot of "tail" for not much "teeth" in direct combat troops (the artillery does provide good firepower at longer range).
if systems are distributed so evenly by design, they are difficult to tweak for particular missions. An urban offensive situation may want to go heavy on dismounted infantry, keep slow heavy armor and not bring in much artillery. A blitzkrieg type breakthrough might want to load up on tanks with some mechanized infantry. A static defense may want to load up on artillery.
This 2017 paper about countering BTGs: Defeating the Russian Battalion Tactical Group. has a different diagnosis of built-in organizational weakness, which also seems related on size vs over-generality: all that artillery (+AA) leaves not much capacity for maneuver/contact combat troops like infantry (and armor), i.e. a little bit of a glass cannon phenomena, according to this paper.
So, has anything like this been done at scale before?
German WW2 Kampfgruppe seem like an obvious match, but they were adhoc formations, based on what was available. They were not pre-planned, were composed of different units and they scaled up and down the unit sizing - for most of them, they were way over Russian BTGs in size. Early WW2 German combined arms capability was also stellar and still informs US land warfare doctrine.
Another, certainly less fortuitous, historical precedent was the French pre-WW2 tendency to distribute armor throughout standard infantry divisions, which gave up the opportunity of deep battle/blitzkrieg combat tactics envisioned by Tukhachevsky, Guderian, Liddel Hart, De Gaulle and all.
I can't think of anything else equivalent to BTGs in non-expeditionary, peer-enemy, organization in modern Western-style armies aiming for maneuver warfare. But I would also be interested in hearing of cavalry/infantry/artillery combos, at the battalion-regiment level in pre 20th century peer-opponent warfare.