2 (re Canus) I do not believe we will be able to convince either Sombraluz or Canus to take any sort of concilitory action first.
Why not? Sombraluz said we would be treated as a hostile prisoner when he thought he was in control of the situation, but that's changed drastically.
I would not be surprised to see some kind of timeskip message. ("It's ten days later. Sombraluz and four guards open your cell, and explain that you are to be repatriated to Higan as part of a treaty agreement between Higan and New Kosa.")
I can promise you that Purvis Does Not Do This. The largest time skips we get are when we're sleeping. I would actually suggest going back and
reading through all the games in this timeline (I can't find Barren Path anymore ;_;) that led up to this one, because I suspect your past experience with text adventures are substantially different from how Purvis runs things and it may lead to mistaken assumptions about core mechanics. (Or you could just ask him how he generally prefers to run things.)
Relating to the subject of game and parser meta, I can practically guarantee you that this game was meant to be solved as we are, with only Kasen and rebels in tow. This isn't at all difficult for the parser to enforce, either; Yumemi can (and, storywise, should) just refuse to send us back to Gensokyo until the Kosan problem is solved, as she has no guarantee we won't simply run off from her once we get back.
3 (re Gensokyo) Kisume has already gone on a "Tour de Gensokyo" when the stakes were much lower and the only objective was finding out about that mysterious agent. We know that Gensokyo has powerful residents; those residents could be multiplicatively more effective working together than working separately; they could be much more effective with foreknowledge of an invasion and time to plan; and I would assume that Kisume would be able to reason this much.
This would also require convincing basically all of them that we're believable in the first place, and that the very high risk of death is worth taking. This Gensokyo is not one giant happy family; different houses have different agendas and may or may not participate even if they believe us. I would put money down on this Eientei not caring, for example.
4 (re Kisume's goals as I see them) Her primary goal is to prevent the invasion of Gensokyo. Secondary goals are: to return to Gensokyo, preferably alive; to improve the situation in Kosa the way she would want it improved if she were living there. All other goals I view as tertiary, and I do not believe we may learn any information from anyone that would change or override these goals. This said, I have been viewing as foolish the actions you (Kilga) have been taking, which I interpreted as entering into conversations hoping to learn goal-influencing information, which would preclude pathing the encounters to best support Kisume's goals during the most critical phases.
I can list my goals, if that would help.
- Stop the invasion, duh
- Restore Kosa to democracy. Yumemi sprung us from prison and has done a bunch of shit for us since, we owe this to her. She is also our ticket back to Gensokyo and requires this goal to be met, so it should be done regardless for the sake of satisfying her.
- Bring Sariel to justice. I suppose ultimately it doesn't really matter what happens to her, so this has the lowest priority.
- Minimize loss of life, including Empire forces (this includes the Emperor). Not only should this be simple common sense, but death is
very heavily frowned upon in this series. We have had at least two immediate opportunities to kill in previous games, and in both cases there would have been severe, world-dynamic-altering negative consequences (as I found out in postgame by asking). Murder is out of the question unless absolutely necessary and I'm extremely far from convinced that we've hit that point.