Astronomers need to be in on it also. They claim to routinely use RE models to predict star positions and the positions of other stellar objects.
Most major navies need to be in on it especially if they ever use submarines. Even high flying balloons/stratelites sending false GPS signals won't matter for the submarines since the subs when underwater can't get GPS signals. Of course, prior to LORAN/GPS pretty much every ship needed to be in on this conspiracy to navigate properly. (fun fact, there is no way to make the Earth flat such that the Mercator projection of the apparent sphere gives you correct navigation).
Also, whoever is busy manufacturing and maintaining all these stratelites needs to be in on the conspiracy. That's got to be quite a lot of people. (Maybe they are part of the big NASA conspiracy that is in the know?)
Anyone we are missing?