Suggestions and Subjective Guidelines for Custom Story Level Design

[Radiance]

To add up, I'm trying to set up an combat type for Amnesia and SOMA. It must follow some rules

• -> it's consistent in stealth and defense/attack mechanic
  
• -> it's challenging
  
• -> it's has risk and reward feel
  

A type of gameplay when player feels he plays a chess game with the monsters in that particular level.
What I've could thought so far is some kind of environmental hazard technique in which you use the acctual level environment to your advantage.
So, this would directly affect the level design what PathOS and Robosprog talked that every level must have it's own functionality. Player should pay attention to his/her (I don't know if any of women population is lurking on this forum) surroundings and temporarily or permanently entrap an opponent.
Second,
for Amnesia there could be some magic/fantasy oriented mechanics and for SOMA steampunk/cyberpunk theme with the heavy usage of particle and physics system.
Also, it would be great to think defense gameplay system which we haven't seen yet in history of gaming.