An annoying and embarassing failure happened on the second mood - the human caravan arrived super early (seventh of galena) and thus also left super early and i completely flubbed trading. I was getting swamped in "couldn't find seed" messages because the isolated sub-fort _did_ have insufficient seeds of some types, but still.
And then a farmer/woodcutter went moody and it turned out they'd immigrated with glassmaking. Great stuff, since i've no sand at all on the site and didn't have any raw glass left over. The would-be glassmaker finally went melancholic two weeks before the dwarven caravan showed up.
I've had two moods in the sub-fort by now and they both succeeded, in spite of requiring materials and in one case even an anvil sent in by air mail. The only connection between the sub- and the main fort is via ballistic minecart: the main sends the cart off a 30z high mountain, it then flies ~95 steps with an apex of z17, lands on a track in the sub-fort, goes through a processing loop intended to sort incoming carts by weight and gets launched right back out of the sub-fort after passing the loop. On the return, it only reaches z7 or z8.
Carts that are moving at more than one tile per tick respect pathing obstacles (i.e. they don't teleport through closed doors), but will only activate pressure plates if they landed on them at the end of a step. Plates "teleported" over will not fire. The design would need to be much roomier if launching off ramps didn't split cart speed into a vertical and a horizontal component, while the vertical component of a cart's speed isn't converted back but simply lost when landing on flat track; the cart went off the first launch ramp at ~2tiles/step, landed at 1,5tiles/step in the sorting loop and arrived on the outside at 1tile/step. Each jump reduced horizontal speed by roughly 30%, or division by sqrt2. I'm not 100% certain, but it seemed that a dumping track stop built on a teleported-over tile actually worked.
Such high-speed carts aren't much use for data processing apart from simply transmitting a message: the cart passed through the whole sorting loop, returning on the second-to-last door, and landed back outside before the first plate it had passed over had time to re-set.