I'd love to be able to blacklist by quest id so I don't have to remember which NPCs offer breadcrumb quests that lead you to a level appropriate dungeon (so I could just auto ignore that quest but accept others from an NPC).
That is a feature already provided by Blizzard, and QuickQuest will respect it.
I like the speed gossip feature, but sometimes right after accepting a quest a gossip option pops up so that NPC can put you on an automount/flight somewhere. It would be nice to have it stop before accepting an automatic travel path.
This one is not easy to implement, it requires hard-coded information about every NPC that offers such an option, as well as localization for every single language the game supports.