We need the ability to share tiles with friendly aliens and/or have the emitter change function when they go blue. What I've seen happen with friendly aliens is they prevent your workers from improving around the city, so you build the fence, then they can permanently prevent you from improving the 3rd ring (if you took the trade route protection) because they run out of hexes to occupy. Once they are packed between the fence and the coast, they are there for good. You should at least be able to move civilian units onto hexes occupied by friendly aliens. Another potentially more attractive option is have the emitter disperse them (similar to the fence) once they are blue instead of damaging them, even if it takes a couple of turns and even if you have to pick one alien at a time to "yell" at. This will be another reason to have the emitter on the tech web and buildable.