How about a difficulty rating for questions?
How about being able to sort questions by the OPs ranking? That way I could for example find easy questions to answer or difficult ones to chanllenge myself...
I think it would be difficult to automate this:
Consider a user who has earned a lot of rep on tag
So then we would consider using only the rep of the OP earned from questions tagged with
So the next thing that I can think of is that the difficulty of questions increases with the the number of views the questions get, while remaining unanswered. That is, if more people have seen the question and it is still unanswered, then all those people who have seen the question are unable to answer it. Therefore, this must be a difficult question. Note that there are assumptions built into this method: no other activity (flag, vote to close, etc) is performed on this question. But then, what happens if it's an overly simple question that nobody wants to answer? What if it's a bad question and we're waiting for clarification from the OP?
Ultimately, I think that with some (or a lot of) heuristics and some AI classification methods, this might be doable, but not without a high computational cost, which is why I don't think it will be implemented. Still, I think this is an interesting idea