I just thought of an idea what do you think
I've always found alliances quite annoying as you can get dragged into wars that you don't want to be in, and I find defensive alliances not much fun so I thought of this idea.
Keep defensive alliances as they are, but if you are on really good terms with another race you could form a full alliance.
In a full alliance you are obliged to help defend your ally if he is attacked, but also if one of the allies wishes to attack another race then a popup window will appear and you both have to agree to it. This stops allies being dragged into wars that they don't wish to be in.
Also If the two allies are on really good terms with another race they could invite them to join the alliance and form a multi-species alliance. If three species are in an alliance and one wishes to attack, it should go to a vote and the majority decides whether to go to war (think it's better to do a 'one member one vote system in this case rather than influence points).
Races in alliances should get extra trade bonuses because as the races trust eachother trade will be conducted faster (fewer border controls etc) And also should recieve counter-espionage penalties as agents will be able to infiltrate easier.
If races become full allies a popup should appear where you can give the alliance a cool name such as the 'Terran - Torian coalition' or 'Drengin - Yor - Korx axis of evil!'