The thing is, the Scorn ever since all the way back in Season of the Hunt, have shown signs of having Culture and intelligence. This is especially apparent in Kells Fall where we see the Scorn Musician. They can be reasoned with, but Fikrul was a Fanatic. Had Crow genuinely tried to replace Fikrul, we could have probably seen a good Scorn faction… though that might create tensions between our current Alliance with House of Light.

Fikrul even made it a point that the Scorn could build and sing. The ones under the Witness' influence were not able to, reduced to mere vessels for its will, but the Scorn under Fikrul have been building towards something resembling society. As you said, Fikrul was a Fanatic, and the power of the Echo made that fanaticism even worse, not to mention his conclusion that Uldren is truly dead, and Crow is just a "dead thing" in his body. As for a non-hostile Scorn faction, the biggest question is who would be the head of such a group? The Scorned Barons that remain will hate our guts for giving Fikrul his final death; Skolas is in a similar situation, given the Guardian is the one who killed them originally. A new Scorn character is the best option, but that would likely be under extraordinary circumstances.

Fikrul is dead for good now?

Didn’t you beat the finale Kell of Kells? [spoiler]Eido creates a serum that can kill Fikrul once and for all. We inject it into Fikrul. The Echo chooses Eramis as its wielder. She uses it to purge Nezarecs influence from Mithraaks, curing him. Mithraaks is named Kell of Kells and Eramis leaves with the Echo to go back to Riis to rebuild with its power.[/spoiler]