I would request an option be added to AGOL map properties that allow for members of the same group to be able to separately add and save layers to a shared map. Last week I shared an AGOL web/map in a major earthquake exercise with our National Guard as part of our group. We were in a distributed environment and needed to add realtime data layers that were developed and then could be shared out with the other members of the group. Not really conducive or needed to track me down as administrator of the group to save map and thus allow additional layers to be added as they were developed. Seems like an option could be added to the map properties that could allow for this type of sharing if the owner wanted to set it up like that.