If Capitol ships could dock with any station and trade cargo than this could seriously screw up the economy.
I propose that Capitol ships can only dock with shipyards to unload goods.
And there should only be like 3 shipyards per nation, and 1 for grey.
Now sure Capitol ships can get loaded up with Moths, fly to a station, unload with Moths.
That would encourage group/guild trading.
And it'd be more fun/profitable.

Good or bad?

Yes, I like it. Or, in a similar mindset, unloading could just take time. Say, a day or so.

Good.

/me pies kix

Kix, you ignorant cad, the economy changes are being done with the capships in mind, as well as other things; what you're suggesting (a Guild docking a capship, crashing the prices of all the goods in that station) is not going to be easy to pull off.

That said, only the biggest stations should have capship docking capabilities; small stations like the barracks in Ukari L-2 shouldn't.