Krampus and Apocrea events both introduced stages that required strong parties to run with minimal loss/ gain at all, hiss.
Krampus took it a step further and validated full bombing, normal damage, and Omega Shell in one fell swoop.
I hope that the proposed "challenge mode" will be a refined version of this. There's a lot of potential here, devs, hiss. Make full use of it. I'd personally like to see more grueling levels with heavy payout.
I'm starting to think that the "challenge mode" is actually a new kind of danger mission. if they would rotate apocrea, grinchlin assault, and maybe another one, they would be at a high level compared to other content, providing unique challenges and stages that you can screw up even if you know what to do. that would even give some sense to the event alchemy machine and its debris.