I really would like to use this but having only one global refueling stop makes this basically unusable with different train configurations.

Could any station prefixed with "Global_FuelStation" be a refueling stop and the suffix (if any) used to specify the train layout. Like "Global_FuelStation LC", "Global_FuelStation LCC", "Global_FuelStation LCCCL", ...

When a train needs refueling match locomotives with L and cargo/fluid cars with C. If a stop for the specific train exist send it there. Otherwise send it to "Global_FuelStation" if that exists. Last report an error every few minutes if no refueling stop exist for the train.

Hmmm, this isn't a bad idea. I get around this by making sure my locomotives are always in the same spot - so I have a 1-4 (LCCCC) train, and a 1-8-1 (LCCCCCCCCL) train, and if needed I can do a 1-8-1-8-1 train. Then the global fuel station just has the fuel inserted into those specific spots, so it never gets inserted into a cargo wagon.

You could, in theory, also filter what can be inserted into cargo wagons by middle-mouse clicking the slot in the cargo wagon, so that fuel can't be inserted into the wagon. Then if you have 2-8 (LLCCCCCCCC) and 1-4 (LCCCC) trains, the cargo wagon on the 1-4 trains would have it's slots filtered to only accept whatever that train is suppose to pick up, so that it can't get fuel inserted into it. This only works if each train only picks up one type of good though, since the slots can only be filtered to one thing.

I don't have time to work on this right now - if you want you can make the changes (and upload them), I don't have any restrictions on what people can do with my mods.

I'm using LTN so goods change for trains. But LTN stops output the train composition for up to 32 carriages. Takes a bit of combinator logic but you can enable the inserter for any spot that has a locomotive.

But I don't want my LC trains to go to the LCCCCLLCCCCL refueling stop and block the whole stop. Then I would need multiples of them. Better if LC trains go to their own refuelign stop as they take far less space.