Well let me see, I guess stats weights, openers, 3.4+ BIS now that Creator is out and done, maybe a rough overview of how the job plays. I think you can't go wrong with general purpose information like that. There's really a ton of things to cover if you want it to be a comprehensive guide - but that role has mostly been superceded by people publishing their own guides (on google docs or what have you).

Might be helpful to have a link to resources like the MCH discord server too, a lot of people hang out there these days, and you often get some pretty good discussion going.