To the first point, about the Neretzes Hei, yes and no
If you read all the talks the imperial does are simple: Drusos Neretzes, the old Emperor before Arenicos, disgraced the Empire by loosing not only the campaign (which by the timeline, indicates the empire was in a deep crisis) but also the old Banner of their Hero and Founder. The split on the campaign is due to the indecision of Arenicos Pethros to marry Ira to someone powerful or give her the support for the Empire, or simply choose another heir (probably he hope for a son, soon), the Istiana thing, she was a spymaster, so she had connections and since working directly for the Emperor I'd say access to funds to do her plots as long didn't connect to him, maybe she was the one that easier the way for Arenicos' murder, that I'd love to know about.
That's what I think, the clan Neretzes is disgraced therefore to not face execution or exile as would be the norm (Roman Empire) they gave their support to another in hopes to restore their power one time
But I agree with you, they should elaborate deeper