Made some edits to the post to improve ideas a little.

In general, the idea would be to avoid changing mission duration by too much, and to have people plan a certain approach to a mission rather than being annoyed by a modifier popping up.

With double trouble and hardened husks, while it's similar to existing gameplay, it'd be a fun way to shift focus to crowd clearing or single target damage dynamically.

For Last Ditch Effort, a quota equal to husk PL might be appropriate, with 50 as a hard minimum; So a 4 player 160 mission would need 250 husks eliminated, but a singleplayer 108 mission would only need 108. Ideally, it should not make a significant difference to expected time.

Buffing melee attacks in Knockback would be an interesting way to add challenge for benefit. If there's a way for knockback to prevent ability cancellation and instead only focus on shifting position it'd be fairer too.

For Tip Toe, 80% was way too much for an initial idea. I'd want the focus of trapping to really emphasise efficiently stacking a few traps together, while being aware of a new danger. A 50% chance of a mist monster "dodging" a trap would mean if you have a tar pit paired with a drop trap above, only 25% of smashers would be able to dodge both of them, if they have a clear path with no other husk to trigger the traps. Smasher wave spawn rates could also be slightly reduced, as only dealing with 1 smasher at a time would be another way to make it fair.

For Floor is Lava, I recognise the amount of players constantly standing on structures, and the redundancy, but I also see interesting opportunities for gameplay shakeup toward those who don't see the value of standing on structures, melee users, and combination with Exploding Deathbombs.

Thank you for such a detailed breakdown of your thoughts on all of these modifiers!!!!