Yes, an event.
What it Is
setBrickOwnership would be an event add-on that would set the ownership of whoever clicked a brick to said brick.
Uses
+For Medieval RPGs where you can own your own chunk of land.
+For non-CityRP city RPGs where you can own a plot of land.
+Setting ownership to non-existent IDs (Or Badspot's, etc.) to restrict building on certain areas to everyone, including people with your trust.
Whatever else you may think of...
How it Should Look
Example:
onActivate > Self > setBrickOwnership [BLID] [CheckBox]
Basically, if you check the check box it would set ownership to whoever clicked it. If you leave it unchecked, it would set ownership to whoever is in the BLID output parameter.
Suggestions and improvements are appreciated.
Issues of Abuse
For one, anyone can save a build and load it without trust.
Anyone.
Next, you really shouldn't fully trust people who would abuse it, anyway, and even if they did abuse it, it would be one brick at a time. If they did this to a baseplate, you could just negate it by doing the same event or loading with no ownership.
Therefore, the abuse is no greater than what anyone could normally do.