It would be great if trade played a bigger role in ES2 -- I believe it is a large motivator for diplomatic relations in real life. But since the galactic market is usually (almost) empty, and AIs usually ask for ridiculous prices, trade currently effectively boils down to a) selling your overflow ressources on the galactic market and b) trading a bulk of your overflow ressources for favors/techs. Actually getting a strategic or luxury ressource you need via trade is in my experience practically never possible.

It would be nice if trade for strategic or luxury ressources was actually a necessity, i.e. ressources were more rare, but more easily traded. Something along the lines of "Hey, I have a titanium deposit that gives me 10 per turn, but my neighbour has hyperium to spare, so we will establish a trade relation that might blossom into an alliance later".

But to that end, both a more open trading behaviour by the AI, and a "ressource per turn" type deal would be hugely beneficial.