Hi everyone, so I've read through this whole thread and thought I'd sign up and account and offer some solutions that haven't really been discussed.
-Lets put it this way, Species A and Species B are both trying to colonize the same system, which perhaps has two habitable worlds of whatever variety. Species A lands colony first, but a sphere of influence is not immediately established. A couple months later, Species B lands a colony on another planet.
-Species A is obviously going to finish its colony first (depending on modifiers, whatever those may be). But instead of just kicking Species B out of the system when that colony is built, there is a short period before a sphere of influence is established, say 3-6 months. If Species B manages to complete its colony before that timer runs out, then the system becomes Contested. If the timer runs out before Species B completes its colony, it is kicked out and the Sphere of influence goes to Species A.
-A Contested system could be represented on the galaxy map by having both empire colors appear as diagonal bars in the sphere of influence. Both species will now have several options of how they want to proceed. Both have a claim on the system as well as a CB on one another. So the first option could be that they go to war over the system. Under the war goals, the aggressor can decide whether they want to kick the other species out of the system completely, removing the population from that planet; or enforcing their claim and bringing that colony and its population under its control, conquering it basically. And from what I understand, the defender can choose either war goal as well.
-It would be nice, however, if there were more diplomatic options to deal with the situation. Reasons for a more diplomatic approach could be that the species could be potential friends and allies, and they want to avoid a war that would sour relations; one side is stronger than or equal to the other and a war would be very costly; or one or both sides are pacifists and just want to avoid a war at all costs while still keeping control of their colony.
-Diplomatic options could be as follows: One side agrees to give up their colony and leave the system completely, moving that population elsewhere; One side agrees to cede the colony over to the other with some form of compensation; both sides agree to joint ownership of the system (this option would not be available to xenophobes or fanatic militarists, maybe others; or maybe only available to xenophiles; or only available with high enough relations).
Now of course, this only deals with one system being contested. I'm not sure how it would deal with multiple systems in the sphere of influence, like in the instance of the Blorgs. Perhaps it could be the sphere of influence that is contested rather than just the star systems. This is just my idea of how to deal with contested systems without one side just being magically kicked out or having to go to war. I DO want the Sphere of influence to block other empires from just colonizing inside my territory, but if I really want a system and the AI is already colonizing it, I also want a chance to get it without necessarily starting a war. Even though I'm not pacifist, I'd still like some diplomatic options available to deal with territory. I'm also aware that if some of this doesn't already exist in the game, its unlikely to be added before release, so perhaps these options could be considered for an expansion or in a later patch.