Aliens shouldn't get upset for encroaching on my terf.
Basically, right now my understanding of the diplomacy model is that any time your ships are present in a system where an alien has a presence, it drags on their relationship.
I understand the reasoning behind that, it's not polite to send a fleet of battleships and park them next to the alien's homeworld.
But then again, if an alien colonizes a system in MY home system, they shouldn't turn around and complain that my ships are going in and out of there.
This is especially noticable if you have a "multiple Empire from the same system" game going on. Like the old Exodus game where you have 5 Empires. I noticed this especially once empires started building ships, suddenly all relationships started to tank dramatically and soon my game was stopped as every few minutes one ship ran into another and due to the the difficulty of actually getting diplomatic teams going to preserve this relationship.
I propose the following ideas. Maybe these are in place (/shrug) but if not, perhaps they should be.
1) x2 "sensitivity" in homeworld systems. A bit of a tangent but any relationship penalties should be doubled if it's next to the alien's homeworld. Bonus points if it's an alogrithm based on proximity to your homeworld and there's. For example, if it's a system smack dab in the middle it's not nearly as big a drag as going to their homeworld or a system clear on the opposite side of the galaxy (i.e. one you have no business dealing with).
2) You cause NO drag when it's in YOUR home system. SO if you're on earth and they colonize mars, they can't get upset that you're in your home planet.
3) You cause no (or highly reduced) drag when you were there first. If you already have presence in the system when they come about, they don't really have a good reason to complain, do they.
4) All this is the same on the flip side. So they cause no drag to your relationship if it's in their homeworld and/or they were there first.
On a semi-unrelated note:
Allow teams to be made with people with 0 skill in that area. Right now it is very hard to get espionage or diplmat teams as you have to wait and hope for randomly generated diplomacy people. Why can't you assign a few "trainees"?
I think the penalty is inherent as you have an inferior team as they'd contribute nothing for the team score, but especially for diplomacy it can be years before you can get even a single diplomatic team together, meanwhile you have veritable armies of currently useless, "NO SKILL" commanders. You can assign a commander with no skill to other positions (staff positions, army and naval ships) but you can't assign no skill members to teams? They can't apprentice with experienced members and learn over time?