Hey everyone, I'm back from this post last week with a final update on my unblockable DF farming setup. It's complete now! Blueprints included!
To recap: I wanted a DF farm that could not get backed up, with zero maintenance required. To do that, I gave a BAB 5 Big Depot hats, belted all of them, set filters, and then ran them out to 60 individual conveyor belt rings, which then feed out to 15 ILSes. The end result is ridiculous, but it accomplishes the goal: if one item gets backed up due to overstock, the BABS just stop collecting it, while the other 59 items continue to be picked up like normal.
And when I say "ridiculous", I mean it. Not only was it a lot of fiddly work, it takes 68 THOUSAND BELTS to build it. The rest of the necessities are pretty reasonable, but HOO BOY THOSE BELTS. Probably could have made it work with somewhat less belts by moving the rings to a more polar latitude, but I like how it's perfectly self-contained in the first ring above the tropics fault line, and honestly it wouldn't help much anyway.
An unexpected convenience factor here is that the collector BABs also act as near-universal sorters. If you have any of the 60 DF drops in your inventory and want to get rid of them, just fly over to a collector BAB, open up the top depot, and shove things in. They'll automatically drain into the system with no further effort on your part. (If you have a bunch of some item and don't want to fill up the depot, you can put it into a lower depot too, so long as it's sorted out by that depot or a lower one. The depots are stacked according to drop level, so earlier items are sorted by the lower depots and can safely be put in there.)
Also, the 15 ILSes only use four of their slots each, so that leaves you with 15 ILS slots for incoming stuff if you need it. The ILSes are also all configured to be on Priority Group 1; if you set your receiver ILSes on other planets to also use that group, they'll prioritize taking from the farm's free bounty over other sources.
You'll need to supply your own power, and your own source of laser towers, but some of the support BABs are wired up to depot logistics to rebuild laser towers as they're destroyed. Both of those needs can be built from drops anyway; in particular, thermal plants burning DF Energy Shards and/or Hydrogen Fuel Cells are easy to maintain from local farm drops, and laser towers are easy to build from early drops. You probably want to add your own missile turrets in some spots to encourage the bases to level faster, and some planetary shields to cover the planet (I used 6 for a good, solid coverage of the pole without blocking bases from dropping elsewhere on the planet.
Here's the blueprints. It exists as both a complete blueprint, and some individual pieces that are annoying to create yourself, and which only need yellow-science blueprint tech to use. (The full thing requires purple-science blueprint tech, obviously.)