I have to agree with Ayden, that the GAC's following (or even attempting to follow) the Fellowship model would be overkill. There is no way we could or should go down that track, and that is from personal experience.
Pua and I (as leaders within our sections and ex-Fellows) were asked to be mentors for some Pacific Fellows in ICANN58,but I found it impossible to keep up with the huge workload that was expected of the mentor/coach before, during and after the ICANN meeting. We did what we could but we both found that the expectation and demands of the programme were just too much on top of preparing for our own workloads on the ALAC and GAC (and we were in the middle of the Review as well). As a volunteer with other personal commitments at the time, I felt swamped and I know I did not do justice to what Janice and Siranush were expecting of us.
For At-Large. I suggest that the more measured mentoring approach, that is more manageable for both parties and follows the guidelines that have already been suggested and provided by Dev and his onboarding team, is the model that we should continue to support for newcomers to our community.
(The BC model sounds very friendly and coordinated, and based on years of experience as a mentor with Marilyn in charge. Who could take on that role for At-Large?).