No TR so far, but IIRC TRs are more or less embodiments of concepts which have dual natures: one nurturing, and one destructive. The TRs usually start off in its destructive phase, only by collecting 108 SoDs that the TR unleashes its nurturing phase, as is most evident with Soul Eater (by resurrecting Gremio) and Punishment (by removing the damage penalties for Lazlo).
The problem with Nagarea is that they're a theocracy, which means someone like a High Priest is ruling over them. I think Zelant more likely fits
I love the idea of the return of the True Wind Rune, but the other True Elemental Runes must be present, I guess. Then maybe we could have all the heroes from previous Suikodens together as guest stars, so to speak, like what they did with Tir in II and Lazlo in Tactics. Of course, bringing Frey could be a problem because he will no longer have the Dawn Rune.
It's not all about knowledge, but it helps.