Here is a novel idea

 Opportunistic switching.

Except for pre-set trains like the log train, ore train, and coal drag, make up any train you want with available cars in the yard, not longer than 6 feet. Travel around the layout, switching at any or all locations you want. At the end of the run, all cars are stored in the main yard.
 
The benefits. NO PAPERWORK, no lost cars, no switching errors, every train is different, everyone gets to make up their own train, NO PAPERWORK,  no checking starting locations for all rolling stock, multiple car types per siding, do as much or as little switching as you want, oddball loads are OK, NO PAPERWORK, could have yards at each town, (not easy to plan for with a card system), quantity of each type of rolling stock not important, Could start and stop trains at any yard, NO PAPERWORK.

Drawbacks. Congested main yard while making up and breaking down trains. Realism is lacking, but you almost need to go to car cards for that. Would need to adhere to one train per town rule. More bottlenecks. Lack of structured running, except for unit trains. Only a few pre-set trains ready to be run.

Any thoughts or comments, send to ljbrinker@yahoo.ca