Loading and unloading stations along with the components broken out into parts to use. Missing fluid loading and unloading which is a pain to make nice.
They are chainable ie you can connect the combinators to the next train stop and set the constant signals to the matching materials it will expects to disable stops that cannot unload a full train worth of materials except the first stop to prevent it from not being able to access any stops. These designs were stolen from Circuit Book (Green/Red/Blue) and adapted for top and bottom unloading as well as sending materials forward and backwards relative to the train. Loading is much more basic as it just uses averages to get it to load in an even way. I definitively lost some connections while working on this.