No A/B switch needed.
Put a 2 port coax plate next to the amplifier plate. Move the outside coax to one of the coax connectors on the new plate. Run a short coax from the other new plate connector back to the original amplifier plate. use a short coax to jump from one of the coax pair to the other.
With the jumper in place, you have exactly the setup you have now. Remove the jumper and you have a home run line outside for your satellite antenna, then connect the receiver output to the tv through the other coax.
