It's late so I may be missing something, but how would an RF modulator be used? Unless those other three rooms have older TV's that do not have direct composite inputs? And would you use the composite output connections from each Joey/Hopper to feed a dedicated extra TV? Or a bunch of Y connectors from one Joey or Hopper to the other three?
For me, I tapped into one of my Joeys to add an additional "fake" TV. Meaning, I have a Joey feeding my home theater in the basement via the HDMI output and then hooked the old tube TV we use in the workout area to the Joey's other output which is SD composite (found some old 50' composite cables to cover the distance). Don't care about video quality on the tube TV. But as you know, you'll only be able to watch on the "fake" TV whatever you are watching on the device it's hooked up to. For us, no one would ever need to use both the theater and workout TV at the same time so it works out fine.