I think the best thing to do would be to build the new house right onto the "back shop". It wouldn't be the easiest way but better in the long run. I think if they didn't they'd end up wishing they had.
As many locomotives as they operate, a roundhouse like that would be very nice to have. Have one drop pit in the house as well as in the shop. You're talking about hiring 5 or 6 more guys though. Just to do jobs within the roundhouse including cleaning it.
It sure would be nice though. They could install air fittings all over the shop along every stall and that way they could use that to grease the rods rather than have the air reservoirs charged with air all the time and having to run the air compressor on the locomotive.
Kinda fun to dream some times!
Kevin Bush