2) Morale system v1 - This was just basically an adaptation of what happens in AD&D (which is how I would classify LostSoul's mechanics too). It requires managing morale as a separate system and has the same disadvantage as the Intimidate system from 4e, it creates a 'second path' to defeating monsters, with attendant problems.
I definitely used AD&D for inspiration for my morale system. One important thing to note is that the result of a failed morale check is that the NPCs need to change tactics; it doesn't necessarily mean surrender or retreat.
There were a few design notes I wanted to hit:
1. Act as a flag for the DM: the situation has changed, the NPCs need to respond to that. It's easy to forget about changing NPC motivations in response to the situation with everything else that you have to keep track of, and making the check is a way of reminding the DM that this is important.
2. Act as a way for players to overcome an encounter that's not killing everyone. I've done this as a player, especially when outmatched.
3. Related to #1, as a way to remind the DM that the NPCs are supposed to be characters and not game pieces.
I think there was something else but that about covers it.
Anyway, in 4E I would probably put this in the encounter design space instead of as a global rule. The system would include rules on how to handle this extra dimension of an encounter, and the Monster Manual entries would include suggested or default morale options.
Just brainstorming here...
You set up a number of conditions (three should be enough) that describe the nature of the encounter. When the condition is met, the NPCs make a morale check and the corresponding effect is gained. In the monster entry there's a default set of conditions and effects (maybe the effects are set by level).
Goblin Default Conditions & Effects:
1. Leader Bloodied:
2. Outnumbered:
3. Stole Some Loot:
It's been too long since I played 4E to offer any effects, but these would take into account what a goblin can do and make them more interesting. You could have an Insight check reveal this information as well.
If you had a Spider Queen encounter where she's guarding her eggs, she might have a condition where, if the eggs are threatened, she attacks the PC threatening the eggs (or maybe halts combat or something, like the Alien Queen in Aliens when Ripley is threatening the eggs with her flame thrower). If they are destroyed she goes into a frenzy and only attacks the closest PC. If she's bloodied maybe she grabs some eggs and runs, I don't know. Whatever will make it interesting.
You could do some fun things with monsters, like the classic example of presenting garlic or a holy symbol to a vampire.
Some powers, especially psychic ones, could apply morale conditions.