Filtering Active Assembly Table Editor

On the current project I am on, I am running into the issue of not being able to filter the active assembly table editor. This is an issue when dealing with shared content types across multiple sites.

Example: Navons.
To deal with the table editor showing all slots visible to navons across all communities, we have one slot for each of the needed template areas. Once a banner, footer, left nav, right nav, has been set on the navon at a folder level, we any pages underneath it use that inherently if it does not have something to override that slot. The issue comes when we can place different pieces of content from different sites into these shared slots.

Site A has content type X which renders template 1, in the Header slot of the navon. Site B shares the navons, and uses content type Y with template 2 in the same slot. Members of community A have visibility to see content type X and template 1, but not content Y and template 2 (vice versa for community B).

When someone from Site A goes to edit a navon, they can search in the table editor for content from their site, AND Site B. Even though community A does not have visibility to see the type or template that can be placed in that shared slot, they are allowed to search for it in the table editor and place it in the navon slot (if a content type is allowed to be shared across site, we allow visibility for both sites). Once published, this causes odd templating to occur and things to look weird.

I was curious if anyone else has dealt with a similar issue, and if anyone had any code that might be able to restrict that search from the table editor to prevent this.

John W.