First: Why are Reading West, Reading Upper Triangle, Reading Traincare West, North Acton, and others incorporated into the map and GWE world, respectively? Second: Will we ever get an expansion of the maps (Rapid Transit expanding to Magleburg, NEC New York expanding to New Haven or Boston, GWE expanding to Bristol, Weston-super-Mare, and/or branch lines such as the W&E Central branch from Slough)? Third: Will Crossrail be added soon (Paddington to Heathrow)?
Can't answer 2 or 3, that's something only the future will tell. Personally I hope that we see route expansions in the future but I guess the first priority for them is adding more and more content (new routes) so the game can grow and expand maybe later. Some of the locations you listed are used in scenarios and some services go to or from the traincare depots.