Would it be possible to rank and then sort questions on a scale of easy, intermediate, and complex? It would help if there was some definitive system that would be used for ranking questions (perhaps including: external sources; multiple opinions; controversial questions; high risk of issur involved; etc.)
In theory, this is possible on very technical sites, backed by some kind of complex machine learning. A system could learn that questions about .. let's say ... regular expressions are inherently harder than questions about array indexes. That would be interesting, actually really interesting, but the pay off for the amount of research and work that it would take wouldn't really justify the cost. That's not to diminish the actual usefulness of such a feature, it's just not capable of justifying the immense cost of developer time to pull it off.
If this were to happen, we'd almost have to stumble on it accidentally, while trying to do something else related to our tag prediction and other systems that help put stuff that interests you in your feed and on the front page.
This could be done using tags, but you'd be getting pretty heavy into meta tag territory, something I'd strongly advise against.
Declining this not because it's uninteresting or not useful, but at this point, it's not really something we'd be able to take on.