Posting my prediction now, pre-Deltarune Ch3&4, not even as a heavily evidenced theory, just a sudden realization based off vibes while analyzing the new Sweepstakes web pages:
I think the Weird Route will end in a softlock.
Deltarune is a love letter to RPGs and every quirk of storytelling AND mechanical play that makes them what they are. Toby has always loved meta games before he made his own, and the Sweepstakes are RIDDLED with references to glitches, mods, softlocks and more.
What if there is "Only one ending...?" In the sense that there is only one final boss you can defeat and one way to make the credits roll by following the intended narrative on a normal route? (Of course the smaller choices you make along the way still matter as long as the characters matter to you, but the overall result will be the same.)
Maybe the Weird Route will not be an "ending", in the sense that the credits haven't rolled, the "final boss" isn't defeated, and you can still boot up your save just fine - but you cannot progress.
Whether that is because Noelle becomes some kind of angelic, unbeatable guardian of a frozen "Angel's Heaven", a Dark World just to her liking that you can never seal due to her power surpassing your own (in an Undertale style consequence of leading her down the Weird Route in the first place)...
Or because of something even more insane? The Twisted Sword can only be crafted with the Thorn Ring, but gives Trance DOWN when equipped to Kris, which would imply less control. The only thing Noelle seems sure of in the Hospital after a Weird Route is that something is wrong with her friend, and she is going to figure out what. Seam once wielded a seam ripper, for when "you're too far along to simply pull the threads [of a story?] back out". And who KNOWS what Ralsei or Susie will do on an extended Weird Route. Maybe the Weird Route will involve Kris shaking us off and breaking free, leaving us with no way to play.
Or maybe it will be neither of these and some third option, but regardless! I think the ultimate irony of the Weird Route would be if it doesn't properly end.
The player, in trying so hard to contort the narrative and game into a different ending, does nothing but break it. Congratulations! You changed your fate! You found a different path and made your choices "matter"! And now you have nothing. No closure, no accomplishment, only a save forever stuck until you wipe and start over. (And do it right this time!)
That's my suspicion. Anyway, wish me luck getting the Shadow Mantle, because I'm gonna be playing 3&4 blind first, and I am TERRIBLE at missing stuff, so...
