Looks good. Has some good potential. I wouldn’t bother adding more track to be honest. On a small layout, it’s tempting to cram in too much track. Sometimes less is more! If anything I’d feed that siding to building 5 off the loop to make it easier to work.
Will be fascinating to see what they come up with. Probably not loco-hauled. Something like this? https://www.globalrailwayreview.com/news/115884/hitachi-eversholt-rail-gwr-battery-hybrid-train/
My son is a daily commuter into London (and is a professional railwayman to boot). He has a choice of routes and opts for these whenever he can above more modern offerings!