I think it does.  I was playing last night and was marching towards a research victory and the remaining factions all declared war on me except for my allies.

Though I totally see what your saying.  They did not join forces.  Some were still fighting each other and this attack was not exciting as I was way more advanced.  I even armed my allies to the teeth so we ended up fight much more efficiently then the rest of the galaxy.  It would be cool to have them unite as a coalition against you.  Or you could join one to stop another.  

One thing I am trying currently is a game where I 'team up' some races. 

Borg+Yor

Drengin+Krynn

I may make a 4 way team with all four above...^^^

Altarians+Iconians

This means they share resources and sight and can and should defend the other. 

You can assign teams at generation. Ill report back and see how it works out. 

It would be great if a dev could chime in on this too

 Honestly, fixing the mop up phase, a common problem with most 4x games, would give a game of galciv 3 SO MUCH more longevity. You no longer have that point in the middle of a game where it just starts snowballing in your favor with no return. 

Pshaw? Frogboy? 

This would mimick an actual board game being played around a table.

"Don't trade with him! He's going to win!"

I would totally support that.

Only as long as there is good counter play.  In gal civ 2 there was an event that made part of your empire break off and form a new faction.  But it was random and there was no defence against it, so it could straight up just lose you the game if it took the bulk of your manufacturing worlds which was very frustrating, especially as someone who plays with a slow pace on the biggest maps.

Imo rebellion should be an expansion level addition with depth or not done at all.

While I happen to agree that this would make the game better/more challenging, be aware that this type of AI behavior has often been universally hated in other games.

This is an age-old debate all the way back to the first Civ-style/4x games. 

Some people want a challenging game and they want the AIs to band together to 'not let the winner win'. Other people consider that horrible and that AIs should act 'normally' rather than gang-up on the winner.

EU2 had 'bad boy' rating which everyone hated. Civ 2-3 (and 4?) had mechanics to reduce diplomacy based on 'score'. 

I would imagine making it a configurable option would work too but again, then you have two camps of people again.

I hear a lot of good ideas.  Was thinking how we could add them.

Rebellions, have noticed that there is no penalty for doing things outside your moral alignment.  If you do that enough times some in your faction might feel you have lost your way, your not a true good, bad or pragmatic leader and they break off to form a more pure version?

The don't trade with that guy he is going to win.  I was thinking we might see this when espionage added.  Spies can often plant info, you should also have the ability to warn factions like they warn you.

Coalitions, EU games have it where when multiple nations go to war with others, the best/most powerful nation becomes the alliances lead faction. They set strategy for the war.  In the game this could me, if your are lead, you could mark planets controlled by the enemy as planets to invade, defend.  If your not, you might get missions from the lead faction, like please take planet x in 10 or more turns.  When peace comes, the lead faction does the negotiations.  This is neat, because if you hose your allies and keep all the planets for yourself you might find them turning on you.  There is a historical president for this, many allied nations in WWI felt screwed at the peace table and turned in WWII, ie Italy and Japan were on the Allies side in WWI.