We've seen a handful of alt Lockdown gamemodes, such as hazardous mode and hardcore mode as cycling variants, but we can probably have a lot more, so here's some of those as ideas:

• Players drop a consumable on death instead of a heart
• Invincibility frames are disabled
• Players cannot be flinched
• Shield health is increased/decreased
• Player health is increased/decreased
• Player defense values are doubled
• Unique variants are disabled
• Trinkets are disabled
• Disable locker room equipment restriction

These are just a few ideas of possibilities to throw around and try out as temporary modes. I think removing invincibility frames and flinching would be interesting to see how they play out as players rely on both of those quite a bit, and it would open up other weapon types.