Regular payments

Yes to this in a huge way. Multi-turn diplomatic trade deals are something I've wished for ages.

In the same vein as aquiring small amounts of resources per turn, I'd also like to see an auto-buy feature added to marketplace that serves the same function: to buy small amounts of resources per turn. I already use the market on a per turn basis to buy small amounts of resources, and it would speed up my gameplay if there was automatic "agent" buying things for me while I set the desired resource quantity and the desired min/max price that the "agent" should purchase at.