Ai patfinding is mostly a problem for crew inside ships. Iirc after a scene change crew generally would end up correctly with access to their stations. (maybe because when not rendered they have no collision? dunno). AI ships in my experience don't have issues (they always seem to arrive at their destination), so AI could attack and defeat your city defenses and military bases just fine. Then the only difficult part would be capturing the flag,unless I'm missing something. I don't expect AI emperor to send troops to board my ships (though that would be cool)
Also, if you put a limit to the number of planets, this shouldn't be too much of an issue. (in my example, just 17-20 additional colonised planets). I currently have 16 planets for my main empire in 7 sectors (some cities are just a few buildings, and no cities above 10k inhabitants iirc), 2 for the new empire in separate sector, and 1 Ogar planet (in one of the 7 main sectors). After removing the 4 backup manual saves, my Saved game folder is 1.47 Gb. (Each manual save is about 477 Mb). My game just loaded of a HDD in under a minute. (2nd empire, small 3k city) Maybe with you it takes 5+ minutes because you have densily packed ringworlds, and load the game while your character is in a RW system? My 16 Arc currently only has 1 city and 1 single airport settlement. It makes me think the size of the rest of the universe doesn't quite matter during loading times, only the current system.
Of course there is the question of disk space. But even if doubled it would be about 3 Gb for the saved games folder with a single save. So even if manual saves were also doubled (954Mb), with 7 of those, you'd have max 10 Gb, which is alot, but, at least to me, acceptable.
Also, if you put a limit to the number of planets, this shouldn't be too much of an issue. (in my example, just 17-20 additional colonised planets). I currently have 16 planets for my main empire in 7 sectors (some cities are just a few buildings, and no cities above 10k inhabitants iirc), 2 for the new empire in separate sector, and 1 Ogar planet (in one of the 7 main sectors). After removing the 4 backup manual saves, my Saved game folder is 1.47 Gb. (Each manual save is about 477 Mb). My game just loaded of a HDD in under a minute. (2nd empire, small 3k city) Maybe with you it takes 5+ minutes because you have densily packed ringworlds, and load the game while your character is in a RW system? My 16 Arc currently only has 1 city and 1 single airport settlement. It makes me think the size of the rest of the universe doesn't quite matter during loading times, only the current system.
Of course there is the question of disk space. But even if doubled it would be about 3 Gb for the saved games folder with a single save. So even if manual saves were also doubled (954Mb), with 7 of those, you'd have max 10 Gb, which is alot, but, at least to me, acceptable.