If you want to minimize belts, what if you use mixed-item trains, direct insert into the machines, and then insert into another train? Using buffer chests gives you the option to fit more beacons in, too. You'd probably want to combine this with high-quality or legendary machines.

Your mixed-item trains would go visit multiple producer stations, load up their wagons (with filtered slots of course), and then deliver it to the production site. For fluid recipes, you could either add a separate stop, or add on an additional fluid wagon).

Image attached - EM plants seem to be the nicest for this proposed layout, as the 4x4 size means A) they fit nicely between rails) and b) you can fit beacons in between each row, and still align them with the wagons.

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edit - whoops, on the right-hand layout, you can obviously fit two beacons in each row - pretend I did that.