A well written post with a good level of depth into an important topic. Thank you! If I were to give a suggestion, I would say that I don’t find the title a very good flag of the content.
This isn’t a Task Y (at least it doesn’t obviously fulfil your outlined components), but a small-scale interaction with EA not currently mentioned would be the 80,000 Hours careers guide emailing scheme. This sends you a part of their careers guide each week for you to read and interact with. This supposedly takes 180 minutes to complete over 12 weeks. This seems like it may have up-scaling capabilities, too.
Another potential quick-fix similar to this could also be a more robust internship system within EA. 80,000 Hour’s job board has internships, and we could encourage people to utilise it to help fill some of the place of a Task Y (lower-commitment, can have a clear positive effect, includes career capital).
However, I would stress that neither of these ideas seem like they would completely fulfil the role of a good Task Y.