I think it would be cool if the sleep effect made a player fall over as if they had died, likewise being immune to normal attacks, until another player ran over to wake them up, as if reviving, or until a long timer runs out. When affecting enemies, the traditional system is probably fine. I also had some other status ideas while thinking of what sleep effects might be like.

Blind: Makes the screen go dark or all black, possibly dependent on resistance. It should end up dark enough to obscure the difference between enemies, allies, and obstacles.

Confuse: Randomizes the images for enemies, allies, and possibly projectiles also granting the ability to damage or shield bump teammates.

Fear/Panic: Forces affected knights to keep their shield up, whether broken or not, unless making attacks.

-espil