Well I just so happen to have had a lot of time on trains today, and I'm done with a full re read!
First things first I want to praise you for the richness of the characters you've presented us- Adela, Amalamir and Amalaric in the Kuni wars were very compelling personalities.
The Caoimhe cycle was also very fun to read, and I loved how much it felt like every single one of those characters pops up in other stories. I hope that when the Theuts come along we get a good mythic cycle out of them as well, hopefully with some more fantastical elements.
I do have a couple things I wanna talk about, raise for discussion etc, some are continuity some are just random thoughts.
First let's get through the bits which can stand as independent points-
At one point though you make reference to Saharan sands- without an Arabic conquest of North Africa at some point, I don't see a reason why in universe translators would call the Sahara by the Arabic name. I can't find what the Romans called the Sahara though, so if anyone can help on that that would be cool.
At one point you say:
"Lachtna said. “For the Gaels will drain an ocean of wine before this night is done. Never before have I seen a folk drink as they; even Thor himself would be unable to out drink as they"
The Celtic Caoimhe cycle has a proverbial reference to Thor? How much does Theutish mythology worm itself into these epics??
Amalamirs rage at the Avar duplicity got a chuckle out of me- the way you described his anger made me think he might go the way of Valens, who had a stroke in the middle of a shouting tirade while berating goths.
You've said a few times that you see the dominant form of Arabic in the Manichean communities being a descendant of Sabaean or a south Arabian language in general. This doesn't really fit with the names you've given, which are all very *Quranic Arabic, and most definitely don't have the south Arabian post posed article. Arabic Al-Rahman, South Arabian Rahmanan. I think given the strength of the poetic koine that would give rise to Quranic Arabic in the 6th century already, it kinda comes out of left field to have it be replaced by south Arabian which had been on the decline for centuries.
On the Senate:
"Leading members of the political rebellion included members of the Anicia family, who remained powerful nobles in both the East and the West."
This is from chapter 19. One thing that I do want to flag up is that as evidenced here, the senatorial class in the east and west is the *same families*- in fact the gens Anicia you mention here was related maternally to the then current emperor Germanus. These are the same people, who will move to whichever half of the empire offers better career prospects- a system which otl collapsed in the Gothic wars. There was an offhand comment somewhere that the Romano-Persian wars that were analogous to otls 602-628 saw the eastern empire switch to Greek- I don't think this is possible because the senatorial class must remain able to work in Italy. Also if Italian senators are allowed to muster armies, as you confirmed, I think they'd definitely use them to help the east- if a senator knows that their brother who lives in Constantinople is being taxed mountains because of a war, they'd probably try and help end that war. Forget that, the same senator probably owns a villa in thrace, Hispania, Egypt and Sicily, and he'll want to protect his investment. The Italian senatorial class has the power to do that, so I think would definitely be helping out against the Avars and Slavs. For the east then, this is a brilliant situation as italy doesn't need defending but can still raise troops. Because of this, and as well because the Latin speaking regions such as moesia haven't been lost, the east is a much more Latin beast than otl. I also think it's a more religiously unified beast- monophysites and chalcedonians may differ on a lot but they're at the very least monogamous nicenes- both sides would be a lot more willing to compromise given Arianism as a constant and present threat. All these factors combined with the fact that even though Anastasius and Justin left the empire with a sizable budget surplus, and Justinian never wasted it on reconquest, the east hasn't been particularly aggressive, just makes me think the east has spent that budget on building projects and lower taxes- it must be so much more prosperous than otl. Nevertheless, I do foresee it being a major priority for eastern emperors to kick the Avars out, and maybe even take Pannonia- it would explain the fact that you mention *Slovenes receive Christianity from the Orthodox if an army from Constantinople has just conquered the gepid state.
Despite this, Im not saying that it's implausible that the Persians and Belisarius so quickly conquered Egypt and anatolia- that's just the way late Roman armies worked, in that one defeat leaves open vast chunks of the empire until such time as the army can re coordinate.
Also:
"This, despite the fact that it is likely that no Senatorial families of any standing survived Frithunanths I’s purges following the Fall of Rome."
Unless the east is also affected by this purge, those same families will be clamouring for revenge.
Also:
"Consul Aquila Marcini" given the senatorial class is the same in both halves of the empire and the tria nómina system is... More present there even otl, I think it probably would make sense for it to continue in Italy- perhaps "Flavius Marcinus Aquila"
Oh wait sorry, you confirmed this later on my bad:
"fact that late-Roman surnames continued amongst the Senatorial class of Italy when they were dropped in the rest of the Latin world is but one example of this influence. "
So, two possibilities present themselves. Either the dominant language becomes a Vandalic with a heavy admixture of Berber and North African Latin OR the language is North African Romance with additiona of Vandalic and Berber
My take on this is that even otl, before the pod, the vandal court had adopted Latin as a language of literature- there was a flowering of Latin poetry based in Africanitas, where the Vandals used the Latin language to position themselves as successors of Carthage. Additionally, given that the actual Bible itself is identical in Arianism and Nicene Christianity, the Latin Vulgate was used by the Arian vandals, and I don't see why they would switch to the Gothic Bible, which of course wasnt ever their language. I think the same situation probably exists with the Lombards- they're unable to mimic theodemirs two state solution, so would likely latinise very quickly under the influence of their Dalmatian Roman subjects.
I can understand Gothreike proper having been gothicised as a result of ethnic cleansing, strict use of gothic in law and religion etc, but I don't think those conditions exist anywhere else. Apart from in Gothreike, especially in formerly Roman provinces, it just makes sense for the Arian church to continue to use Latin.
Much as Dal Caoimhe remaining Celtic would be cool, I definitely don't see how they would resist latinising considering they even share the orthodox faith of the Baeticans.
On Arian unity:
"With the support of the state behind them, the Gothic Church soon became the predominant Arian Church in the West, and the Churches of the Vandals, Bavarians, Allemani, Avars, and Gepids came to acknowledge its primacy of place over them"
As I mentioned before, the Vandals always used Latin in their Arian Christianity, and have an older church structure- so this seems like something they wouldn't take lying down. Especially given the insistence on polygamy within the Gothic using Arian church, I expect the more romanised Latin Arian churches to anathematise this as heretical.
On the Vlachs/Romans of Hispania and Jaille:
Do these guys count as Vlachs? No right? Because Sixtus and Bishop Honorius and Eugenius make it seem like the Praetorian Prefects of Jaille and Hispania are much friendlier to the orthodox than the situation in Gothreike proper. As seen with Dal Caoimhe as well, much of their nobility is orthodox (and maybe merging with the senatorial class of Italy/the empire- you did mention that some Italian senators have holdings in Spain, indicating that the Spanish nobility is already going through that process)- this seems like a very unstable religious situation, ripe for intrigue and meddling. The vandals aren't on good terms with the goths, so I think still very well may end up going Nicene under influence from Italy/Constantinople/Dal Caoimhe, but any such move by a Praetorian prefect is asking for a full on war with Ravenna. How then do they manage the religious divisions in their administration? Perhaps a war with Ravenna is worth it to avoid the religious disputes that tore otl Byzantium apart.
This makes me bring up some thoughts on Romanitas as an ethnic identity. For many in the 4th/5th century, Romanos vocitant nostrae homines religionis. The men of our religion are called Romans. All of our Nicene sources make the distinction of Roman/Barbarian essentially the same as Nicene/Arian, Christian/Pagan. But Arianism itself sprung up in a Roman context, and Theoderic quoted Theodosius to the Jews of Genoa- for him Arian Christianity meant Romanitas. Would a Latin noble in TTL Hispania who converts to Arianism be able to see Arianism as Romanitas? Would he be seen as turning goth, or is it just a different way to be Roman?
In Ammianus otl, no matter where you're from in the empire he has a tendency to describe ethnicities as they existed before Roman contact- but will describe Bavarians, Franks and Vandals as Roman in the context of their service in the Roman military. Is a Roman simply a potential fighter in the Roman army? The most consistent marker of "barbarian" fighters is their wavering loyalty- Roman soldiers, whether Frank or goth, fighting for usurper or incumbent, only act for their emperor, and by extension pro Res publica. Civilians are cives, provinciales, sure but never Romani. That distinction is only for soldiers. Is that reproduced here? Are Italian soldiers/potential recruits more readily accepted as Romans because they fight for the state, than say Hispanian or Jaillois Latin speakers who defend themselves from raiders on a more local basis?
I do think though that the references to TTL modern Italia and Naples as states come despite the fact that the inhabitants of these states at the very least identified as Roman for a lot longer than otl.
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