I understand what you are saying ... but isn't it a coin toss whether your diplomacy efforts will work? I mean if it gives you three missions in a row that you can't actually do - all your efforts go up in flames, no?Dan
Actually each AI faction will only give you one mission at a time. What you need to do is strategize which ones you want to do, based on the AI's strength, the ease of accomplishing the mission, and their prexisting hostility towards you.
My rule of thumb was to pretty much do all the 'Give me XXXX number of credit/metal/crystal' missions and very selectively choose which 'Destroy x number of faction y units" I did. Honestly, the loss of resources was more than made up by the AI allies that I earned later in the game. And at one point, I had all of them at greater than 50% 'friendliness' to me.