In my current game, I have a fairly distant neighbor that I'm on good terms with (mutual trade access, I'm sharing my geo data to help speed up improving relationship). They are one of the few AIs I've run into that are actually reasonably decent at spreading out, i.e. they have their homeworld plus three other systems with non-trivial colonies or mining operations. There was one system of buffer (Lakara on the attached map) between their closest claimed system (Eradain) and my closest claimed system (Hawat). Hawat is important to me, as there are two big, mineral-rich and near-habitable worlds there which I am colonizing. Lakara is also important, as it has a gas-giant with 58M Sorium at accessibility 1.0(!) However, I do have a similarly large deposit down in Rigel two systems below Hawat, at 0.8 accessibility, that I have a very large fuel harvesting operation at.
The issue is that my friendly neighbors are now politely suggesting that I vacate Lakara in the near future, as they are now claiming the system. They want it for the same reason I do, i.e. the Sorium, and they just got some Sorium harvesters set up there, next to mine.
Realistically, there's no reason to fight over this. We can both use this deposit without any risk of it running out in the next 100 years. The only reason to fight over it would be to deny it's use to the other, and since we're friendly, that's silly. I'd like to continue making this empire into an ally, as there are three other more hostile empires in other corners of the map I need to deal with.
Given the limitations of the diplomacy system in Aurora, how can I best keep this empire happy? I don't really want to deny them access to the Sorium, which I think is what would happen if I issued my own claim of the system and they accepted. I would be ok with ceding the system to them (given I have lots of fuel in Rigel), IF I were positive that they wouldn't later try to claim Hawat (I don't know how expansionist they are, but their xenophobia seems fairly low since I've been able to get them to like me reasonably quickly). Should I move out of Lakara, but pre-emptively claim Hawat? Would that prevent their trade ships from visiting Hawat if I claim it and they accept the claim?
Any thoughts on how to solve this mechanically in Aurora?