If you go to Don Hensley's TAPLINES website there is a photo of  3 foot gauge passenger cars riding on standard gauge trucks.  I think those cars were longer than the J&S cars.  The train ended its days as a logging camp in Florida.

You can use Google Earth to chase trains.

None of my Bachmann locos have sound cams.

You might use dual gauge track so standard or narrow gauge cars can be iced, or standard gauge track on one side and narrow gauge on the other, and use planks to slide the ice down to the narrow gauge cars

The older car has type K brakes, the newer car has type AB brakes.

There used to be a company named 'Keyport Car and Foundry' or something like that who used to make l&p couplers.  Dont know if they are still around.  Harold Minky used to have an article on making them on his web page. 
My local logging railroad used link & pins (roosters) into the 1940s.

Seuthe makes them

It was originally HOn2 1/2; Kalmbach called it HOn2 1/2, Carstens called it HOn30

It can be difficult, and expensive, to remove existing paint.  Detail is obscured with each succesive layer of paint.  If my loco is painted green with yellow stripes, and I want to paint it red, I will have to undercoat it, and I will have a model with 4 coats of paint on it.  An undecorated model gives much better results.

I own 50 2-8-0s, 35 4-6-0s and 15 4-4-0s.    I bought the first one around 1998.  Out of all of them , I had 1 wire pull out of a tender connector, and one gear wear out.  Bachmann replaced the drivers (free, IIRC) and I hardwired the tender connection.  I cant say a word against these engines, I love them.  The 2-8-0s are great runners and great pullers.

The Crab Orchard & Egyptian used steam regularly into the 1980s.   The Pennsylvania RR used both PAs and GG1s on the New York & Long Branch in New Jersey into the 1960s.

Didnt Atlas make a low-nosed SD 7 or 9 or 24 or something?  Maybe splicing an Atlas cab onto a Geep body would save some work.

An ALPS printer can print in white.  Unfortunately they are no longer available in the uS.  I think Kodak used to make a printer that used white, also. 
Seems I read somewhere that the chemicals used in making dry transfers are extremely toxic, and OSHA or somebody monitors the exposure of people involved in the manufacturig process very closely.  Dont know if thats true or not. 
Scale Graphics Decals is the name of one custom decal manufacturer.  Dont know anything else about them.

There is no mystery involved with electronics.  All electronic components contain magic smoke, which makes them operate.  The key to working with electronics is to NOT let the smoke out.
Someone may have let the smoke out of one of your engines.

Thanks for the pics.  While all the transit agencies in the images use bi-level cars, the model is not a match for any of them.  It does appear closest to the MBTA car.  I believe the models are models of Chinese cars.  I wouldn't let that stop me.  If you like them, use them.