I would scrap the mainline connections to Eastwick and Westham in order to preserve the Inglenooks switching operations in those two areas. Also, I'm not sure what the purpose is of the outer-main passing siding hidden under the mountain? Being under the mountain this track cannot be used as a fiddle yard?
I don't know what the codes might be and I don't know about frostline in your location but wrt the bathroom, there are macerator toilets that pump the sewage through a 1" line and can even pump up to iirc 10" head. They were designed for basement bathrooms in structures where the sewer connection is higher than the basement floor. Could be a way to simplify the sewer line to the house.
Lew