This is not really a good mindset, though. As in, I can concede that it might be "realistic", but only in that people in RL might believe in such a thing, despite any evidence or reasoning to the contrary. (A lot of things are "realistic" in that they happen in RL, but in RL we also acknowledge it to be mistaken and flawed, if not utterly stupid. The International Realism proposed by Quintus van Cinna is an obvious example.)
The flaw in this mindset is "let the ideology burn itself out" requires not only time, but also keeping the people involved powerless for the entire duration. This effectively turns the situation into a sort of incarceration or prison, to prevent any part of that toxic ideology from spreading outside of the carefully controlled environment, rather than addressing the toxic ideology itself. In fact, it's letting that ideology fester by allowing its proponents to come to power, regardless of whether it's allowed to affect anyone else.
As we've seen in the 6.x patches, the Ilsabard Contingent are not interested in doing that. By far what the vast majority of them want to do is go home, because they don't like the climate of Ilsabard any more than the Garleans do. So quarantining the existing Garlean ideology of conquest and imperialism is already rejected for being too much work for not enough results.
And we've also seen that the Ilsabard Contingent, and the Eorzean Alliance behind them, are more than willing to give more power to the surviving state of Garlemald, however rump. That was the whole rationale behind the trade treaty with Thavnair; the Ilsabard Contingent do not wish to be gaolers to the Garleans, and the Garleans want to move towards self-sufficiency. In fact, my own annoyance with that plot point was how literally nobody had evidently thought about reopening trade until Varshahn brought it up; realistically, this should have been one of the first proposals from either the Eorzean Alliance or Garlemald.
Letting the ideology of conquest "burn itself out" is very dangerous, because you need to be absolutely certain that burning will not spread, and that it will burn itself out instead of continuing to burn forever. The more realistic route is through education and de-programming, ie "convince the remaining authorities to play nice". So I strongly disagree with your point 2 as stated, but strongly agree with your point 3 as stated.