shop.

sell and mission access from chests, or chest adjacent to hub or bays.

trade combinators. red and green signals. red, buy this many. lockout for a second or so after a transaction to allow recalculation propagation.
green signal, sell that many.

buysell selection. nauvis shouldn't buy uranium, only sell. vulcanus should never buy tungsten, coal, calcite. I.e. local specialties are sold, not bought.

Missions can request a resource sold by that planet, and buy it for greater than the sale price. Might be unintented. Observed for concrete on vulcanus. Bought 760 concrete for 1520, mission gave 4776 bucks.

why is water barrels an option.
oil as an option makes sense.
starting LDS or plastic would be nice. though working out how to make it was a thing.

was amused to see bulk inserters are useless until researched. not sure why powerpoles are sold.

"sell and mission access from chests, or chest adjacent to hub or bays."
Currently, items in chests are counted for mission turn-ins, but they are not used when selling at stations. I will fix this in the near future.

"buysell selection. nauvis shouldn't buy uranium, only sell. vulcanus should never buy tungsten, coal, calcite. I.e. local specialties are sold, not bought."
This is actually how it should work right now — there might be a bug somewhere. If you can provide an example of where a non-local item was being sold, or a local item was being bought, I would appreciate it. I might need to tweak the lists somewhere.

"Missions can request a resource sold by that planet, and buy it for greater than the sale price. Might be unintended. Observed for concrete on vulcanus. Bought 760 concrete for 1520, mission gave 4776 bucks."
This definitely needs to be fixed. Thank you.

"why is water barrels an option."
I believe water barrels can be useful. At least, I personally used them quite often during my own playthrough.

"starting LDS or plastic would be nice. though working out how to make it was a thing."
Plastic is intentionally not sold from the start, but it may randomly appear for sale once every 15 minutes. This adds a certain challenge in the early game. That is by design.

"was amused to see bulk inserters are useless until researched. not sure why powerpoles are sold."
Try building them from the character's inventory — they should work even without researching them.
As for power poles, I'll tweak the random item lists — they are indeed not needed.

Uploaded release 0.9.109

water barrels. talking about the, you can collect ice.
starting lds/plastic. talking about the, you have it in the hub as starting resources, so replacement of broken collectors is plausible.
bulk inserters. without the first research level, their stack size is 1, meaning they work exactly like a fast inserter.
power poles are, admittedly, slightly useful for circuit wires.

Starting LDS/plastic: on reflection, no change needed. Nauvis sells crude oil in barrels and coal, plus refineries and chemical plants, so plastic — and from it LDS — is reachable;

Bulk inserters: you're right, and my earlier answer was wrong — the bulk-inserter technology itself grants the first +1 capacity, so an unresearched one behaves exactly like a fast inserter. They stay in the shop on purpose: buying one early is an investment for later, once the research lands.