Fiona: Competence and Replacement
Fiona can perform beside Loid under pressure. That achievement does not settle her claim to replace Yor.
Spoilers throughout. This page discusses story events and outcomes.
Fiona's professional ability gives her a serious claim to be useful beside Loid. It does not by itself establish that she should occupy every role beside him. Her proposed replacement of Yor makes that distinction consequential.
A proposed improvement has a person inside it
In the official episode 21 summary, Fiona proposes taking over the wife's role and independently visits the Forger home to meet Yor. The household becomes the object of a personnel decision she wants to make.
The proposal can be considered as an operational argument without assuming it has only one private motive. Someone who believes a mission needs improvement can have reasons worth hearing. Yet proposing a better arrangement also means proposing what happens to the person already in it.
Our reading is that the word role makes the replacement appear simpler than it is. A role can be specified from outside: perform these tasks, satisfy these expectations. A relationship has also acquired meaning through the people who have been present. Replacing the occupant need not preserve everything that made the arrangement work.
The tennis partnership supplies real evidence
The episode 23 synopsis describes the WISE pair countering altered rackets and interference during their match. Their effectiveness together is demonstrated under active opposition.
That evidence should count. Dismissing Fiona as merely disruptive would ignore an ability the story places in action. A partnership that can respond to an opponent's changing tactics has achieved something beyond looking suitable on paper.
The question is what follows from the achievement. Success in a contest supports confidence in those demonstrated capabilities. It cannot establish the quality of a domestic arrangement that has not been produced by the same test. Treating the result as a universal qualification would make one kind of performance carry authority over another.
Useful together does not settle every role
The strongest defense of Fiona's proposal is practical: a constructed family serving a mission cannot be insulated from questions about whether it serves that mission well. Existing membership is not an automatic answer to every criticism.
But a fair evaluation would need to examine the function actually at stake. Greater competence in one setting can coexist with less knowledge of what another setting requires. The match makes Fiona's usefulness visible; it leaves the replacement argument to be demonstrated separately.
This is why the paired scenes give her more substance than a simple rivalry. She has evidence for her confidence, and the evidence has limits. The Yor study considers insecurity within the household. Fiona's proposal supplies the pressure from outside it: the temptation to treat another person's place as a job whose requirements have already been fully understood.