If these get added, not only will it add more difficulty to the game, it will also give more variety to the Clockworks rather than the same Fire, Freeze, Poison and Shock stages, and it will increase the randomness factor in the Arcade, making it more like the sandbox experience OOO strives to turn it into.
In Stun strata, enemies are larger. Nearly every slow-moving enemy can Stun you and some variants of faster enemies can stun you as well. To keep things from getting too annoying, the Stun effect is changed so that if you get hit with a Stun attack, and then if you get hit with another one while you're still Stunned, it doesn't extend your Stun time. The atmosphere is changed to one of ruin and more yellows are used.
In Curse strata, some enemies have attacks that can Curse you. New to the game is the Curse Symbol, a floor hazard which, similar to the existing Fire, Freeze and Poison vents and the Shock panel, will Curse you if you walk over it at the wrong time. It glows when in an active state. The slower enemies like Lumbers and stationary ones like Gun Puppies tend to be the ones who cause Curses. While outside these levels, Curses last upwards of 30 seconds, Curses in these strata will last, at most, 20-25 seconds even in the sixth stratum.
EDIT LOG
Edit: Changed stratum aspects due to flaws pointed out by Almond-Riddle.
Edit 2: Changed Stun and Curse stratum aspects due to critique by Supnaplamqw.
Edit 2.5: For some reason my edits on Stun either didn't show up or mysteriously disappeared. My bad.
Edit 3: Removed Sleep strata completely from the idea. See Almond-Riddle's second comment and my reply to it to understand why.
Every single one of those statuses weren't added in for a reason. Namely, they all shut you down. Adding a stun, curse, or sleep won't just add a level of difficulty, it will add levels that literally cannot be beat.
You also don't seem to understand what sleep does. It renders your knight IMMOVABLE. Not just immobile like freeze, you can't do anything. You can't even GUARD. Even worse, getting attacked will NOT wake you up. So a single attack that puts you to sleep is, quite literally, instant death.
Stun has a similar problem. If fast moving enemies that come in droves like Devilites, Minis or Kats could stun you, they could keep you in a state of permanent stun until you die.
Curse is less problematic than the other two, but is a lot more annoying. Unlike most statuses that only last 15 seconds tops, curse goes into a huge 30 seconds, even for minor curse. So letting your character get cursed once will turn the stage into an agonizingly long game of tag until you can attack again.
This won't make difficult levels. They'll make stupid levels. It'll be like an entire gate filled compound levels.