Let's talk engine servicing...this was a key goal of mine for the layout. In fact, if the entire layout had to be one big engine servicing terminal, I'm good with that--it would be a great layout to me! (actually, Model Railroader DID publish a layout that was just this--servicing terminal with staging--all the rest was left to your imagination. I loved it!)
Anyway, I have reserved a nice-sized section of my 0 gauge, 3-rail layout for the engine terminal with the theory being that engine servicing is a good "switching" industry, It turns out that engine terminal layout and design isn't a "gimme". There's LOTS to think about.
I found a used Bowser 26" turntable at a train show in very clean shape. To go with it, I wanted a great roundhouse, so I got one of Brennan's limited edition models. I added stalls to go up to 7 which s really all I have room for. The turntable is in and the RH is just getting started. I have an MTH Marklin tin plate backshop that has to go in there somewhere (repro). Beyond that, let's see if we can list the rest....
Coaling (with service track for
water (towers or plugs or both)
Blow down wash out
Pump house for wash-out
Diesel fuel, wash and sand
Diesel shop (if space....)
Icing house and platform (if desired)
Terminal light towers
Any shops you want (boiler, foundry, mechanical, electrical, etc).
Specialty tracks--RIP, MOW, caboose, office/inspection/testing cars, wheels
And this is about as far as I have gotten. I'd LOVE to see some pix of your engine servicing areas and hear any discussion that would help me make progress.