Thanks, Krishna.

Tibet et all:

Wondering whether the way Announcements are restricted is a path.

Also two other paths: 1, allowing spaces to set space-specific roles, with one role  essentially having a "read only" status. Or 2, (more promising, I think), in the view admin pop-up, enabling a "who can post?" selection UI with various roles and "everyone" set as default.

I know this could have zero to do with your architecture; just thinking about a UE perspective. This is where my mind goes at night. ;)