Hey folks. Basically, the title. TLDR at the bottom. I'm setting up my automated resupply train. Obviously, I'm using inventory-slot-filters inside the train's cargo wagons. My problem is length of train vs. preventing the outpost receiver station from over-accepting.

I'm familiar with LTN but that doesn't provide quite the solution I'm hoping for. By specializing specific types of resupply trains (i.e. one type exclusively heads to the wall with loads of ammo / repair packs / replacement wall segments / etc. Another resupply train would handle almost nothing defense-related, instead providing roboports / replacement rail (Rampant mod) / miners / pumpjacks. A third train type would simply bring heavy_oil out to supply the flame turrets at the wall, etc.

For any given train, I've mostly worked with only allowing 12 individual species of item to be transported in any single cargo wagon, with 6 inserter-chest combinations per side of the train.

I also know that I could theoretically get up to 24 by loading them with red inserters to reach past each other. But that generates a problem at the receiver outpost.

If I keep myself to 12 species per wagon, first of all my train becomes dramatically longer, and all I need at the receiver is either a purple or a white filter-inserter to unload into red passive provider chests and then simply slot-limit those chests to control how much any given outpost draws from that train's inventory.

I'm looking for a way to be able to precisely remove 12 item-types per side (instead of 6). Red inserters don't have filter abilities. I can double-filter or multi-filter any individual green or purple inserter, however. But then how do I ensure that I won't run into a scenario where a vital component isn't being delivered by the train simply because the first-removed item type occupies every valid chest-slot, whether slot-limited or not? I can't apply slot-filters to the internal volume of the red passive-provider chests because that's not even a thing I've heard about with respect to mods.

I'm tantalizingly close, I'm sure of it. The last solid-seeming idea that I just gave up on was using a filter inserter to remove one cargo-type from the original-6 unload-chests and thus one of the two item types only is in the main offload chests (closest to the train track). I could use either logistics-connect or a red signal wire on the main (closest-to-track) unload inserter to tell it when the outer-layer chests are full and that the filter inserters unloading are satisfied and to focus from that point toward filling the needs of the primary chest. But if I've limited my chest to, say, fewer-than-ten stacks in total, it'll be hard to prevent one cargo type from "clogging" the system and preventing anything else from being offloaded. If I leave the chest wide open, that means that it'll be even more difficult to "dumb-circuit" a few decider combinators.

TLDR -- I'm setting up an automated patrol-train or a resupply train. I can control the train's internal inventory levels by assigning specific filters to each cargo-wagon inventory slot. I can then use that to load a supply train with 12 red inserters on each side of each cargo wagon, knowing that the red inserters will hang once the train is full of whatever item the red inserter is working on.

But I cannot find a working solution to reliably offload such a train at the destination. Any help would be appreciated.

Edit: I'm very familiar with circuit smarts, constant combinators, adding and subtracting read-mode inserted contents, etc.

I'm asking, specifically, if there is a dumb-setup method. I play multiplayer, and part of my design consideration is having it make sense to my coplayers if I happen to be offline at some point.

By only handling 12 item-types per cargo wagon, I can control everything with nothing more than requester chests at the central loader, and slot-limited chests with un-wired filter inverters at the destination, so long as I only ever need 12 single-item-filtered filter inverters per cargo wagon. My hope is to somehow segregate 2 items per unload-inserter, controlling the destination storage with something like stack-limiting the chest.

I'm aware of constant combinator setups and am explicitly trying to avoid those. I suspect that what I'm asking isn't possible and I'm asking for someone to confirm that.

Thanks.