Take two. :P[...]
I'm rambling now, sorry. I'll just throw that idea out there for what it's worth. :P
What I had in mind is this: The Scavengers, the former Watchtower soldiers, Ember, if Talmid likes and possibly others (perhaps some people the Thingguys know; maybe the Merry Men or however they were called) group with the KotOS to fight thedude. Meanwhile, you should note this: Half of thedude's army is down in the south struggling to defeat the Corsairs. An important part of the rest is placed in Thunderclap and Orlan, but the rest is spread all over Militiregnum. If we have some rebellions of a decent siz (a relation of King Jork could stir Aquila, a person I discussed with Harold could stir Cheinir and Harold mentioned something about Britay) started when news of the KotOS's return arrive, the army would be forced to remain spread thin unable to crash the KotOS's small force working in Morcia singlehandedly.
Meanwhile, Dewin could put all his strength at one point in order to restore the Enchantment to its full strength rendering all of thedude's technology useless for the duration of the final battle. At the same time, the Nexus Force, either watching the surface closely or having been notified, send a force using PCG teleportation (it's an idea I mentioned a while ago). Attacking Thunderclap would still be hard now, but not impossible.
As for thedude himself, firstly I don't think we should consider him OP in army level, but in hand-to-hand combat level. If he could just crash armies like that on his own, he would have done so already in PD. But anyway, we have JDI (and possibly Ember, though I don't think Talmid meant to have her reappear) to counter him till one point.
This was my idea all in all, I don't think it's too different than what already proposed and entirely possible.
Thingguys' ideas could include the Nexus Force and/or the Dragon and/or something else.
I agree with it.
About that character, anything else I should know? Like a name, or should I come up with that for myself?