I purchased the system recently. It works great for me, saves a lot of time and mess. The only
regret that I have is that I did not buy the system that was mountable in the RV.
I have contacted Thetford asking about running a hose from the Tank valve to a mounted unit within one of the compartments. Their replay was that would not be a problem as long as the pump was below the drain valve since it is gravity fed. The pump does not pump out the tank, but only takes what it receives by gravity from the tank and then pumps it out to the sewer inlet.
Its pretty hard to find a compartment below the sewer drain valve, so I end up raking the pump out of the box each time, connecting it to the rain valve and then putting it into operation.