How would you implement stealth?

[Shinobody]

Stealth is a major component of many tactical games (like Commandos or Jagged Alliance), but it barely exists in Battle for Wesnoth.

One implementation I remember was some campaign for Era of Magic where you played as a vampire count, where stealth involved having to kill enemies who see you quickly. I don't think that's inherently a bad idea, though it was poorly implemented in that specific scenario, as you didn't have any units that had specials like Backstab (or Charge or Berserk) that'd be perfect for this, and because of that it was easy to lose quickly due to bad RNG.

So what are the other options? One idea I thought of myself was a dungeon/interior map where you have to stay in dark spots, and entering the light will get you noticed (maybe if you linger for more than one turn?). That alone isn't that interesting, but it becomes interesting if you add Illuminates special to the mix, which creates more of a typical 'stealth game' situation, and creates interesting situations.

Another similar idea I've been considering was completely bespoke scripted setpiece that would create vision cones (highlighted hexes that if you stand on, you get noticed) in the direction the unit is currently facing (opposite direction they last moved from), so you could safely stand 'behind' a unit. Send these units on a scripted patrol path, and again, you gotta a decent stealth scenario.

Then there are of course options that actually utilize the stealth-based abilities like submerge, ambush, concealment and nightstalk. I imagine then the answer is "if you end your turn in sight of an enemy, the alarm rings". Nightstalk could be combined with illumination-based stealth mentioned above.

So question: how do you, or would you, approach adding a stealth sequence to your campaign or scenario?

[Atreides]

Den of Thieves has something like that with Skulk. Hidden while next to a wall during the night.

[egallager]

That one Liberty scenario handled stealth okay

[Lord-Knightmare]

Assassin in the Forest was pretty nice for a stealth-based scenario. You had to snipe out 5 leaders while they battled each other.