Back when I was first learning, and asking lots of basic questions here, I was very happy to see questions posted that I could answer. It gave me a way to contribute something to a site/community that helped me. As my level of knowledge increased, I was able to help with harder problems. I even gave bad advice a few times, and benefited immensely from being set straight.

An additional site runs the risk of fracturing the community and depriving all sites of the critical mass they need to be self-sustaining, useful communities. IMO, It would be better to focus on improving PM.

So, if we accept that one site is better (which you really needn't), apply your ideas to PM, we'd update the UI and separate/track content by "difficulty level".

Modern UI

PM my be old-fashioned (sooo very 2001!) looking, but it doesn't rely on buggy javascript and AJAX to add flashy features that die on certain browsers or slow-connections. This is a pet peeve of mine when it comes to StackOverflow. In some ways the interface is very nice. But it is fragile. If an upvote request has an error, I can't vote or see comments until I reload the page. I frequently have problems reading comments on nodes when using a slow internet connection.

I would be open to UI improvements that do not make Javascript mandatory. Stack overflow's node editing interface is great. I'm not sure how well it degrades w/o javascript, though.

Tracking PM by "Difficulty Level"

IMO, it would be sad to see perlmonks tracked by user-level. It would deprive future members of the opportunity to learn and grow organically in an open, level community.

I could see adding some kind of "difficulty level" tagging to nodes as part of the moderation system, that would allow users to easily filter their view if they so desired.

I wouldn't have used such a mode early on, anyway. I read nodes and discussions I didn't understand, but doing so helped me to grow and guided my investigations. Now, I often read "basic" nodes, because sometimes I find a great insight or have a basic misunderstanding of mine dispelled.

If you believe a tracked interface to PM is important, talk to the pmdevs and sell them on it. Also, I suspect that you would need to be willing to do a good chunk of code to the table.

Conclusion

While I disagree with your ideas, I am gratified to see your interest in improving PM and working for the benefit of the Perl community. The cooperative exchange and development of ideas that makes a community strong.