Shadow Construct - Research

My research has revealed the following considerations I wish to adapt into my level:

Ensure there are no avoidance paths in the level (routes by which the player can avoid all obstacles). The solution to this problem is to make sure each part of the layout is challenged at some points.
Ensure there’s no clear vantage point across the whole level. Sightlines should be carefully created so that no critical path can be viewed from any one point. I should also include such viewpoints within any sweep of floodlights.
I might consider making the security measures go into alert after one system has been triggered.
I should make penalty time interesting and make any waiting time/cooldown engaging with some interaction. One solution might be to make an ability which blocks sightlines. The cooldown decreases, depending on how full the player's detection bar is.

Some general principles:

Stealth games are generally pull systems. The system doesn’t change until the player interacts/manipulates it.
Stealth should be up against significant barriers/obstacles/puzzles
There should be approximately 3 - 5 main paths to any major part of the level. There should also be 1-2 minor paths for each main path
There should be significant use of vertical navigation.
Security should escalate slowly, over time.

AI:

Guards typically have three AI-states, which operate alongside the larger gamestate, but on an individual level for each instance of the guard based on player-action. These states are:
Idle: Unaware, patrolling predetermined paths. (Sneaking state only)
Searching: Enemy unaware of player, investigating source of sound or distraction, altering line of sight to affect a certain area. (Sneaking & Fleeing States)
Alert: Enemy actively hunting down players. (Fleeing state only)
Instantly failing the player for being detected isn’t good design. There must be a way to absolve failure and move between the two states in the loop.

Detection:

I might like to set a detection distance on cameras and sentries
Should I implement sound? Can the enemy hear me?
How does the UI indicate detection? I should introduce an indicator to the UI.
Is the alarm state global, or does each obstacle operate discreetly and independently? An ideal solution might be a hybrid - human obstacles are global, mechanical systems are discreet.