Yeah, Alexeia doesn't care much for the legacy of Andreas Niketas, since his example is increasing the probability of getting her brother-twin killed. Keep in mind this is a woman who lost her father when she was young, had her husband killed in front of her, and now is watching her mother waste away. That leaves only her brother, so naturally she and Venera are protective of him.
There is approximately a 0% that a successful Senatorial coup would lead to a Roman Republic. As has been mentioned, 'Republic' is a dirty word with foul connotations in TTL Rhomania. Also a concept of Rhomania without an Emperor is completely utterly foreign to every facet of Roman society. People may fight over who is the monarch, or how much power the monarchy has, but no one, not even the rural dynatoi, question its right to exist.
Having a Republic isn't impossible ITTL, but the only way Romans would pioneer it would be French Revolution style, which admittedly is an intriguing idea.
It's ironic; Nikephoros has become Herakleios. Because of his physical weakness, he has enemies trying to kill him. And even if he wins, he still has to deal with his broken body.
On the Bulgarian defection. I realized that I need to have them join the Allies to avoid Nikephoros just defeating them in detail, and forgot to write that in. I'll go edit the update and have it be five tagmata siding with Venera/Alexios.
Apologies on the confusion. Tagma is singular, tagmata is plural. The two tagmata in Egypt are the Egyptian and the Augoustamnikai. To avoid writing the later out, when I'm referring to both I call them the Egyptian
tagmata. That's what Andreas of Egypt took to the Peloponnesus.
Serbia is a compensation for the unexpected support Nikephoros got from the tagmata. The plan is for a few years down the road, perhaps as a preliminary to the Hungarian offensive, to charge Vukasin with something and use that as an excuse to depose him. And while Vlachia would try to draw in an independent Serbia as an anti-Hungarian ally, an independent Serbia would also sever any land connection between Hungary and Rhomania, significantly decreasing the odds the two come to blows.
Saluzzo is simply put, sucking up to Manfred. By emphasizing its ties to the Empire, it significantly increases the odds that Manfred would view a Milanese invasion as a direct attack on his authority.
The Herakleian Wall is about halfway done.