For couplers, I have 3~4 systems planned and they'll only allow coupling with like units. This is to simulate how you have different companies vying for different standards. Then there will also be vehicles that have universal standards, like the majority of semi-trailers. Converters will be included too.
Freight will only connect with freight, and pax will only connect with pax. However, multipurpose locomotives with push-pull in mind will have their own coaches. Then there will be 2 or 3 different systems for multiple units.
Road trains are also part of the plan. I intend to have a nice selection from scooter to road train.
The vehicles won't be 100% analogous to their real life counter parts. This is because world wide standards are not the same. However, having a large selection of vehicles to choose from your preferred fictional maker is intended. All companies and products will be fictitious, but you can sort of guess their real name.
There will also be vehicles that don't exist yet or at all, depending on deficiencies from the real stuff.
As a general rule for all vehicles, there will be a product cycle.
Prototype or experimental unit
Revised or Refined batches
Upgraded or Modified from existing
Depending on the batch, there will be various perks or flaws, which might later have an upgrade to fix it. Generally, most batches will only have a 5~7yr life before it is retired and the next batch is made.