At first I got a boner for this game but then...
http://www.ign.com/articles/2014/09/25/total-war-attila-announced
Attila and his forces are not a faction in the traditional sense and can’t be played. They’re more like a force of nature that sweeps across the map, destroying and spoiling everything they touch.
bwahahahahahahahaha
Seriously? In a game where I'm trying to blob across the map anyways why not just let me do so? You can actually make that shit challenging, I'm sure it was not just some walk in the park for Attila in the first place...
I guess I leave my TW experience with Empire and Shogun II. Only played Empire due to interest in the time period. Only way I'll play a new TW is if it takes place sometime in the 19th century but all signs point to that not being something feasible in the first place.
I was done after Napoleon though I played it for only a brief period.
I did my best to work with ETW for the same reasons you had, the time period, but the lack of growth in the series really hurt where it's just shallow conquering of increasingly fewer and fewer regions of the map. What really killed things for me was France and Spain proper being reduced to two provinces each (Gibraltar being Spains second one).
It was after that I dropped them and finally learned Paradox games, which despite their issues, provide enough depth to make up for the shallow combat mechanics.
I'd imagine it would be fairly difficult to actually balance Atilla in the game. I haven't looked at the period for awhile, but the only reasons I can remember as to why Atilla was thwarted from actually conquering the Western Roman Empire was the fact that they were much more valuable as an intact golden goose (at first), a combined Goth/Vandal/Roman alliance which beat them a grand total of once, and by the end of it, simple logistical limitations (they were nomads, and as such did not have any real supply lines to keep their armies fed, instead choosing to forage off of the land, which eventually grew unsustainable), disease, and essentially being bribed by the Roman Christian Church to just go away.
Guess it could work if you implement all of this into the gameplay: make food gathering a much more limited and difficult-to-maintain tech tree than the other factions, maybe do what Alexander did and have Atilla being routed/killed an automatic game over, maybe tie army morale with just how much plundering and looting they're doing, so if they spend X amount of turns not killing shit they'll start growing restless and either rebel or desert, etc.
Everybody lived off the land back then as a given. A logistic trail was limited to the Romans and even then it was relied on when on the march.
What prevented them overrunning the WRE was simply Attila's death and how it sparked both a succession war (something with Attila possibly faced in his youth himself with his brother Bleda) amongst his sons and a general rebellion of their thralls that were only kept in line by the power and personality of a strong Hunnic leader. It was a terrible moment for him to have died while the Hunnic Empire and its conquests weren't consolidated yet a reason why Attila backed off from taking Italy, it was too much of a bite and he'd need time to order his realm before expanding again, and besides, Italy wasn't going anywhere and the WRE wasn't going to get any stronger in the meanwhile, time was on his side until it he choked to death or was murdered.
The fundamental problem with the Hunnic Empire was it was too large. Nomadic empires always had tribal thralls underneath them, like the Avars who later down the line that kept Slavs, Bulgars and others underneath their rule and was actually the reason they came to rule Pannonian, the Byzantines paid them to take over the region to order it for them (The Avars themselves were most likely vassals fleeing the rule of the Gorturks in Central Asia or defeats foes trying to avoid vassaldom).
The Huns had vassals that were as large as most large, independent powers at the time, like the Ostrogoths, so when a rebellion hit it wasn't just a small pack of tribes getting out of hand but sizeable kingdom-sized powers fighting against them while the Huns themselves were divided between Attila's three sons, who all lacked his qualities and were very short sighted. Whether Attila killed his brother, aggressively or in self-defence, or that he simply died from disease while on campaign, both of them and their antecedents were a least wise enough to keep moving against one another until their rule was firmly established and the dangerous stages of succession were years behind them.
Slightly OT:
The last TW game I played was Medieval 2, and I didn't like it much because of the braindead AI and repetitive campaign, even though I did play Rome a lot. Are any of the later games any better and if so, what's the best one?
The issue is the gameplay is so one dimensional. You can only the paint the map and not really play balance of power much because you cannot release powers to revive them like in Paradox games, unless you take over a region and then let national rebels take over that region (who'll then be at war with you and hate you for liberating them).
TW games are arcade crap without a bit of depth in realism or verisimilitude that even Paradox is able to pull off to some extent.
They should just stop making the series until they seriously overhaul the campaign map gameplay and bring it up to a level approaching Paradox depth before releasing any more games, and that doesn't even touch on the the what is severely lacking in the battle mechanics (which cry out for a return to the old engine and individual sprites not being tethered to their units like they are now, units themselves effectively being the new "individuals" with each member of a unit having the depth they once had that made Rome1s and Med2 combat make the games as a whole tolerable).