I think it’s an excellent idea and even suggested it myself like a month ago, but not on the forum. I do think that it will probably take lots of time creating this block, time which they don’t have at the moment. If you could make a block that works this way and show that it works they might be willing to add it.
One of the main advantages that I see with this is that you can trade in much bigger bulks. At the moment you have to use store traders and they have a maximum of 999 999 which is a really small amount if you want to trade in things like coal ore and iron ore (or later in game any ore at all, really). I think you already listed the other advantages.
It would be nice if it was set up in a way that you see in the rebel trade station where you can select what you would like to trade for, for example uranium. Then you click on the uranium tab and see a list of things the store block buys, then like at the rebel trader you see how much ore you need to sell for 1 uranium. For example you could sell 1M iron ore and get 16 uranium ingots or something.
You could also change to get paid in, for example, zone chips and sell things like ADV3 components, RC, PC etc.
I can see how this would take quite a bit of work to get done, but I think it would take player trading to a whole new level.