We are in the development process for implementing AEM Communities. In our local environment(AEM 6.2) we have setup AEM Communities.
When a new community group is created, this member section is created by default and the sling resourceType is set as social/group/components/hbs/communitygroupmemberlist.
If we would require to customize the Members section and implement custom members component (Extending social/group/components/hbs/communitygroupmemberlist component) then during creation of new Community Group how the new member component can be associated instead of the OOTB social/group/components/hbs/communitygroupmemberlist.
For example if the extended component is under path /apps/<xyz>/components/communities/communitygroupmemberlist. If we extend Forum component then this component can be dragged and dropped in Group Template Editor so that its part of new Community Group.