I am working on #2. There has to be some sort of incentive for the mentors for this to be sustainable. As a mentee what can you provide to the mentor? What do you think will make this relationship be sustainable?
This area is interesting to me - both to learn and teach. In the past I've explored proffered solutions and found them too heavy and too slow. I'm interested in helping make something that has low friction and is more peer to peer - ping me if I can help but I'm sadly reticent to take the lead.
I feel like the best mentor/mentee relationships aren't based on incentives, but a friendship/concern for one another. A small handful of senior ex-colleagues who I've worked with genuinely look out for me and my career interests. It takes time from their day and often unrewarded intros to their network. Aside from goodwill (and maybe a referral bonus if it leads to a job), there isn't much incentive for them.
If we treat it as transactional, then certain relationships will never foster. For example, if some high school kid got admission to a university I went to a few years ago and wanted my perspective on how to make the most of his education, I have no discernible incentive whatsoever to answer (assuming he can't pay me). Giving a quick response is either useless or hurtful without taking the time to understand his needs and wants. But that kid could probably benefit tremendously if someone took him under their wing.
I think some people want to feel they have accumulated a lot of skills and experience and simply want an outlet to give back in a manner that feels effective to them.
Maybe universities can tell their alumni network that if people mentor new students, they get access to premium recruitment opportunities on campus? Or cities can give tax rebates to people who take an underprivileged youth under their wing. Employers can promote more externship/shadowing opportunites and give invites to the employees. Or maybe senior positions at companies should have "train junior employees" as one of their top job objectives, and alter promotion criteria to bias towards that.