If there was a hypothetical judgement scene for Fiona, I'd hope one option was to not judge her. Alexius was doing everything, including breaking the fabric of time itself, to make her give up herself and her people to the Venatori. Against power like that, there no way she couldn't resist the Venatori taking over. And that before Alexius' intervention, she originally risked her life coming to Val Royeaux to offer an alliance with the Inquisition. In short, it's not your fault, it's Alexius'. Get that bastard out here for judgement.
I disagree on the amount of coercion Alexius had available, but I do agree a verdict of not-guilty, for whatever reason, would be appropriate. (I would have appreciated a similar role-playing option in Denam's context, but he was made to be hated).
What I would have appreciated just as much or more is not just the judgement, but to express the motive of why. One of the things about Denam's judgement is that the options changed slightly depending on if you found the corpse of the Knight-Vigilant. I'd have liked it if the discovery of the Tranquil could get a similar response.
So, in terms of mapping, you'd get your
-Basic judgement introduction
-Inquisitor's question, Fiona's defense
-Judgements
Judgements could be along the lines of
Guilty (With corresponding punishment)
-Mage rebellion unjustified (death for leading the Mage Rebellion and throwing the world into chaos)
-Complicity with Alexius rather than help stand against him (removed from Circle, conscript as an agent)
-Selling the mages into slavery, betraying that 'death before freedom' rhetoric of the rebellion (imprisonment rather than the new mage freedoms)
-Betraying Ferelden, untrustworthy (exile)
-(If Found) Failing to protect the Tranquil under her watch (Tranquility)
Not Guilty (No punishment, with Follow-on Dialogue for justification)
-Mage rebellion justified
-Blame Alexius
-Need for reconciliation to move on after the rebellion
-Saw the future which she was a victim, not complicit
So a Judgement in which the player can express a position on Fiona independent of their views of the mages, with both pro-Fiona defenses or anti-Fiona judgements depending on the player's position.