Looks like there is plenty of work ahead and supplementing the advice given above you might like to consider:- Me being old fashioned, and perhaps in trying to keep the cost down I have used, over the years, the Peco PL 20 switch to isolate any area you wish by cutting the track and more particularly with keeping 2 locos active on the same line. I notice you have several terminal lines which could incorporate this scheme and I have used magnets between the sleepers to uncouple automatically, then isolate the loco, for carriages/wagons to be taken away from the other end of the set up. Or perhaps, for steam, with magnets, an express loco to pull up in an intermediate station to auto uncouple and be replaced with a fresh engine. It all works, just a thought.