The idea is like this...
Instead of building a trade center in your factory, you will have to rely on neutral natives that are randomly spawned on the map. It is ok if they are just the "market" entity without any other living things.
Just like the villagers in Minecraft, you can exchange items with these markets, but each market can only exchange a certain type of item. For example, the market at north can exchange 12 Copper Plates into 5 Steels, while the market at south can exchange 20 Advanced Electric Circuit into 1 Alien Artifact.
The exchange rate will differ. Some markets can give you better things with the same cost. There will also be some special items that you can obtain only by trading with certain markets, for example, 50 Steels -> 1 Crystal, then 100 Crystals -> 1 Advanced Personal Laser Defense Part, and finally 10 parts -> 1 Advanced Personal Laser Defense.
The aim of this mod will be to encourage players exploring, searching as many markets as possible and connecting them with trains. I expect players feeling satisfied when they finally find a special market, like when you find the Ender portal in Minecraft.
Technically, I am not sure whether it will work or not, but here is my thought:
Each market is an assembling machine and has a fixed recipe (set by script when it is spawned?).
Floating text may be used for showing the items it can exchange and provide, like StickyNotes.
Each market is connected with 2 inserters, one for input and one for output. You drop items to the input inserter. It will insert them to the market and then output the exchanged items to the output inserter. It will then drop them on the ground and you are free to collect with your own inserters.
(But if you can insert items to a neutral entity with your own inserter, then there is no need for the neutral input inserter.
)The markets and inserters are destructible, so players will need to protect them.
(If custom artwork is used, please make sure it matches Factorio's art style. More specifically, the view angle should be correct.
)Thanks for reading. Hopefully we will have such a mod in the future.
