Since she is an outlaw in Tevinter, I can really see her becoming a companion of the next PC as they are likely to be acting from the shadows as well.
If we're going to have a more mature woman as a follower, I'd prefer Maevaris for multiple reasons that I really don't want to to clutter this thread with. I don't see them having two such women, no matter how different their personalities, as followers in the same game.
It is odd because, whilst Dorian says Aexius is acting out of character in joining the cult, given what we are told about him in WoT2, it actually makes sense that he might have been drawn to Calpernia even without the promise to help Felix.
I disagree. I think desperation is the only thing that led Alexius to join Corypheus, and I don't for a minute think that he believed a single word of what he says in that "Tevinter will rise from the ashes" speech he gives in the Redcliffe throne room.
Dorian's Alexius, the man "he admired above all others" (even over his father; that's saying something), would have likely seen through all of that garbage
if he were in the right state of mind, but we know that he was not; he was in the ripe condition to be manipulated.
In the Redcliffe throne room, Dorian says to Alexius, "Alexius, this is exactly what you and I talked about never wanting to happen. Why would you support this?" Really, what other reason could there be other than what I stated above?
To go off into a tangent about Dorian for a brief moment... again this plays into Dorian's fears of temptation. Here were two men he greatly admired, who taught him principle, and they each disregarded that principle when circumstance gave them permission to do so. They were
weak. Part of Dorian's fear is that he thinks he will also succumb to temptation, because if these honorable and principled men did, why wouldn't he do the same?
The one that seems out of place is Erimond but he seems a separate thread that Corypheus has set up since he appears independently of which path you follow...
Erimond wants power for his own self and to be on the winning team, that's all. This isn't about Tevinter pride, jingoism, or anything else. It is all about his own power. While Calpernia might have been the leader of all the Venatori, it seems that certain key members -- Erimond, Alexius -- were empowered to lead their own groups, seemingly on their own. We never hear of Alexius or Erimond reporting to Calpernia or taking orders from her, and they each appeared to be in charge of different aspects of Corypheus's operation.
To address your point, I can see Erimond chafing over being superseded by a former slave, but he might ultimately just look at it as biding his time until he could eliminate her, or focusing on the end goal, thinking of his ultimate leader, Corypheus. Such would seem a very Tevinter way of thinking, to my mind.