I finally got to play with the new Factorio 2.0 trains and managed to get a logistic system working.
I ended up using 12 combinators for a requester and 8 for a provider, with a single cable connecting all stations.
The trains stay empty at the depot and are dispatched only when required. If there are requests pending they don't need to go back to the depot.
Since the content of the train doesn't have to match the name of the stations mixed trains are possible, but only going from one provider to one requester. I did this to carry different quality items with one train.
The only problem I know of is that if two trains finish unloading in the same tick and a request is open, they'll both be sent at the same time messing up the system. I'm hoping it's something that won't happen, but it can be fixed with another combinator in the requesters

I wrote all this to see if anyone managed to do it better, I want to know how much of a brainlet I am.