The hardcore questing mode mod is a wonderful progressive questing mod, but I feel as if there are key features that are missing to the questing capabilities that could be added.
Proximity quests: Sometimes, you don't want someone to kill a sheep to complete a quest, just sheer a sheep. So this kind of quest gets triggered when you get close enough to a specific type of block or entity.
Window-of-opertunity quests: Sometimes you don't want people to complete quests out in the day or at night. So this let's you control when quests can be completed from specific days to specific times in a day.
Structure locator tests: Some quests might want you to raid or visit a location, but that location changes with different seeds. This do-hicky finds a specific structure like a village or stronghold and assigns the player to find it. Alternatively one can set a certain amount of kills to it, and toggle the ability to tell if there's any un-open chests in that area too.
Automatic quests: Mainly with reputation, there's a problem where you don't have to turn in quests if they don't benefit you. However, with automatic quests, you'll get what's coming to you one way or another.
Reward chests: Another item actually, not a kind of quest. This chest can be bound to a player and once done, players can choose to send their excess rewards and reward bag loot to that chest instead of their inventory.
Villager quests: A new type of quest. It begins by finding a villager and trading an item with them. Then it ends.
Multi-block quests: These quests require one to build a structure of blocks in some formation (note this is only usable for known multi-block structures, you can't build your own)
Directional quests: Like a quest with requirements, but this allows one to complete one quest, then another, then the first quest again but only after the second quest.
Effects reward: Now for doing certain tasks, you can receive status effects. So completing some quests can reward you with instant health.
Decaying reputations: You can now change repuations to decay or accumulate over time.
Boss battles: Once this quest is accepted, a boss will spawn, kill it to complete the quest.