Things that come to mind:
- Alternative Fire Mode Support for Weapons (Right Click)
- Monster Multiple Attack Support
- Allow Monsters to Pick Attacks from a List
- Could be based on Conditions (Player is Near or Far)
- Could be based on Chance/Weights
- Such that an enemy could Melee if you are close, Shoot if you are far, and maybe sometimes throw a Grenade
- Monster Factions
- Hostile to Player
- Hostile to other Enemies
- Friendly to Player
- Friendly to other Enemies
- etc (may be good to implement as a list of factions you are friendly, neutral or hostile to?)
- Monster Infighting
- Could work as a 'threshold' of 'patience' for enemies to turn on each other if their own faction keeps hitting them like it does in DOOM
- 8 Rotation Support for Attacking and any other States (Necessary for seeing Monsters fight each other since they may not be facing the camera anymore)
- Support for 'Patrol' Area for Entities to generally attempt to stay within, such as losing interest in chasing the player if they are too far from the Patrol area, walking around randomly in the Patrol area or by configuring a Path/Schedule.
- Friendly Entities that can Follow the Player and stay in their vicinity.
- Could just be an extension of enemies with a 'Player is Ally' faction.
- Could work by setting an area around the Player as their 'Patrol' area.
- Could have some kind of 'teleport' rubber banding if they can't follow the player for some reason.
- Able to attack factions hostile to the player.