is there a final bp for this? Not a final BP as you need 2 decider and one arithmetic combinator and it depends on your station layout how you want to organize them. I blueprinted only the needed combinators for a loading station. With that you can adapt your station layouts. 0eNrdmF2ymjAYhveS22JLA...

Now that I think about it ... it might just be simpler to wire the six chests per cargo wagon together, and output their contents to an arithmetic combinator. Divide the total by the amount that one cargo wagon can hold, and output that to its own distinct signal. Do what was suggested above, and c...

I tested your setup for setting the train limit. Unfortunately it doesn't work because while the loop for calculating the average is running, it is outputting higher numbers for some ticks. With how train limit and slot reservation works, this is enough that trains will route to the station even aft...