There are probably many designs like it, but this one is mine
What this is: a pair of configurable station that can keep an outpost supplied with any items that may be required.
There are no practical limits on how many different items can be ferried, beyond train size, and this station can easily be extended if necessary.
Configuration is simple: set a signal in a constant combinator for what item and how many you want to provide to your outpost.
No need to set filters on the wagons or inserters, and no need to set requests on the requester chests. There are two constant combinators which means up to 36 different items, but you could add more (why?)
On the supply (main base) side, the requester chests request twice as many items as specified from the logistics network.
This is to ensure the station always has extra for the next train. The train is loaded with the amount of items specified.
On the demand side, the station will only be enabled if the outpost needs any of the items specified.
Only the items that are needed are unloaded.
The stations also include chests and inserters for barrels, this is to ship light oil to your flamethrowers
Blueprints
Supply side https://pastebin.com/Y90jT255
Demand side https://pastebin.com/2Y8sUerP
Caveats!
There are two major caveats:
1. The train will be loaded with slightly more items than are specified, which means some slots can go to waste.
2. If the train is undersupplied on some items, it may fail to unload the items it does have.
The first one happens because all the inserters are working at the same time, and because of stack size bonuses.
The second one happens because we feed all the signals for the missing items to the filter inserters, to determine what items to unload. The inserters will use the first 5 signals that are greater than 0. The order seems to be the same as the crafting menu, and the magnitude of the signal does not matter.
The issue is, if your train is undersupplied with 5 items or more, that happen to come before the items your train does have, the filter inserter get stuck on those 5 items. For this reason I think it would be best to always oversupply your train a little.
This is also why we use filter inserters and not stack filter inserters. Stack filter inserters only allow one item to be filtered at a time.
I've not found an easy and clean solution to either of these issues, would love to see some suggestions!
Disclaimer: tested in a test world with cheats enabled. I don't know yet how this works in practice, but I plan to find out soon.
