I plan to buy Intrigue before xmas, but here's few experiences from the late game (recent patch, Crusade), maybe it's useful:

1. The AI is super-keen to spam shipyards -  I see planets almost "encircled" sometimes by various civ's shipyards. IMO would be nice if that is handled better

2. Late (turn 250+) AIs hardly build new starbases anymore to get resources that either pop up from events, or to reclaim them when bases are destroyed. Wondering if they lack admins. 

Otoh even with resources on "uncommon" they have some huge stockpiles of some resources, but completely lack others (and due to the above seem to make no effort to get them).

3. Re the AI surrendering, I had it off in my most recent game, but here's few ideas. Don't just simply destroy a surrendering Civ's worlds, rather:

- turn all their home worlds which they colonized themselves into dead worlds with randomly turning some into extreme worlds (toxic/radioactive/etc.), asteroids or resources like thulium

- do similar with planets they had conquered, but with random chances to have minor civs/pirate worlds/or even different major civs emerging on some of those (explainer: "the X settled on this lost world of the former Y" etc.)

Dunno how feasible this is, but could make it more interesting to have surrendering switched on.