We already have !stats, and it's amazing. I thought up another cool concept where you're able to design an arbitrary quest in order to use the Quest Helper to track your progress. For example if you're going to grind for a rare item, you could create a "kill 100,000 <monster>" quest and just have the Quest Helper open as you grind.
I won't go into details on the NPC in this post; if there's interest in this feature we can then start thinking about the details. I do have some ideas.
I'm thinking you should be able to create up to 3-5 (or so) concurrent custom quests at a time and the reward, if any, should be negligible. You should be able to set it up as a kill quest or an item gathering quest, and the quantity limit should be relatively high. Even better, you could be able to set it up as a combination of kills and items, that way you can entail all the relevant data you may want to be tracking from a map in a single quest.
I understand that it would be a big project.
To reiterate, !stats is amazing and I'm happy we have it, I still think this could be a fine addition and it is non-intrusive for any purist out there wanting to avoid custom content.
Happy to elaborate if there's interest.
Edit: Someone pointed out to me that the quest creation is just an extra step, and I agree. If it were possible to copy-paste the functionality of the Quest Helper and give it a new name, like Progress Tracker, then you could achieve everything I wanted while keeping the Quest Helper unchanged and separate.