I think weekly is a bit too frequent, but I agree that they should definitely be regular.
Regarding witness involvement in spam control, plagiarism, child abuse, etc. and regarding mediation (re: your flagging war point) I think esteemed (eh? ;) ) people of the community can do this. It can be the case that witnesses do this but should not be required of them. To be honest I think the larger stakeholders have more of a responsibility here.
While I don't think much changes week by week, especially on the node reports, the nature of Steemit and that almost immediate drop from attention of most posts after the first day is why I would suggest a weekly post(which really could be a cut and paste when things haven't changed).