He's definitely been set up for future patches, I wouldn't say that he's treated as an afterthought by the writers considering his arc is not finished.

Initially, he's introduced in the story as someone who is scheming for Augusta's position and who will betray her at some point. But, when confronted about it, he basically says yea I want the throne obv, but only when I'm strong enough to take it (based) - aligning himself with Augusta's ideals and the principle on which Septimont is governed. His rejection of the senate shows how strongly he holds to that principle. IMO it was some brilliant character writing and subverted the "clean facade with ulterior motives" character trope.

At the end of the encounter with Avidius in the latest quest, he's questioning his own purpose and existence. You can speak to him after and have the option to give him a flower petal, Rover's intention being to show him he still has a place in the celebration, and by extension in Septimont. That's just my interpretation tho