Just thinking about additional hooks and functions that may be useful from lua,
I don't know if mobs/players draw from the same base class, or are completely separate behind the scenes, so where I mention entity I mean for both.

entity_health
entity_healthAsPercent
entity_attack_target (entityId) (returns target entity for that entity)
player_select_target(playerId) (returns currently selected target)
entity_buffs (as table, buffs/debuffs, possibly multi dim table for buff stats)
buff_cancel(entityId,buffName) (cancels buff)
buff_time(entityId,buffName) (returns remaining buff time)
buff_level(entityId,buffName) (returns buff level)
entity_buff(entityId, buffname, level, time?)

entity_health_hook(entityId, health%)

mob_attackers(table of attackers)
list_players(search radius, as table)

mob_equipment(mobId, slot, operation (add, remove, disable),item Id or time)
This one could be particularly useful, allows dynamic adding/removing/damaging equipment for mobs.
Could be used to make bosses a bit more dynamic, or add interesting behavior to mobs.
If I remember right with HS back in the day you could give mobs equipment in their definitions, which can make for a variety of unique mobs (eg tons of shields, tons of def/off/armour/hull, even negative stat equipment).