I found it strange that I could not properly engage in diplomatic relations with teh AI, now I see it's still a bit rough.
Here is what i did: started a large random single star map with all easy AIs, just for testing the diplomatic stuff.
I noticed there is already an initial friendliness modifier, which gives 10-30% relationship to boot.
Since the AI was easy, I could build up a reasonable number of planets and entrench my empire without fear of being steamrolled by the AI. Then, with a rolling economy i could leisurely build a diplomatic ship and start playing with it.
I picked up the best AI, with a 30% modifier towards me and far enough that our empire borders dont spark tensions, and tried to befriend it. the embassy gave me a 10% boost, and I can temporarily get more 10%, totalling 50%, but that's about it.
I found strange that I could not give missions to the AI I had an embassy. For some reason, completely opaque to me, I could give missions to 2 other AIs (out of 7) which I did not try to befriend at all.
Things to improve: Once I created a mission for one of those AIs, I could not see its values anymore. I had set up a few credits and metal for the ai to kill ships from another empire, but I could not see the exact description (I would call it a mission briefing).
If there is some sort of requirement to unlock certain diplomatic actions, they should show up on the info panel which pops up when i hover on each button at the diplomacy window. right now there is a text which describes little of what I would be able with the button, but nothing about how to enable the button.
The relationship window is also a bit vague, I can see the colored tubes going from one empire to another, and in the game I played a few of the AIs had yellow tubes instead of red (looked like they change colour when relations improve). The link between me and the AI I tried to befriend was yellow for some time, but then it became red (dunno why).
So far it seems a few things which were already in game were 'removed' to be added back on in a more flexible way. So far it seems too little from the player's perspective, I hope more changes arrive soon, and more diplomatic items in the tech tree. Especially, bumping up the AI to make use of the diplomatic options and being more challenging overall. But I am a programmer too, I know that sometimes we need to do some serious plumbing which does not show up on the surface, or at least it takes time until we can bring forward what has been done.
All in all, waiting for the next beta update so that the changes can be toyed with a bit more.