Dilemma HO layout plan

[Brakie]

That looks very good but I do not fully understand how you will run an operating session.
Where do you start a new operating session with an engine and some cars to be distributed and where ends the session when all car are collected?
The tracks at the top right end would be useful to attach a cassette with a train for that purpose but the mainline is at the very bottom and hardly accessible to add remove cars.

Reinhard,I see several ways but,I would chose the Jefferson Terminal Ry or Port Edward RR..A connecting road drops the inbound cars and picks up any outbound cars (0-5--0)..The short line crew will pick up the cars and switch them in industry order and then go about their daily work. A end cab switcher or a road switcher would work..I would probably favor a RS1.

No need for a engine house..The engine would be kept on the bulk transfer track for easy refueling by a fuel contractor.