transparent projects in the world
remove transparent projects for non tribe members
It would add alot to the immersion if you wouldn't see the projects of other tribes. Would make the gameworld much more realistic.
To make it even more interesting you could also change it that only tribe members with the permission to create stuff on tribe lands could see project.
A bonus effect of all this could be a better performance since you don't have to display all the project in the world and you don't have to load them, only the ones in your tribe.