Re: Diplomatic proposal...what to answer ?
 

One problem I have is that when I make treaties, the F@#)#@$ computer can then send ships through my guarded warp ports, in preparation for an attack (I once had a military alliance parter do that).

As a result, I have now adopted a policy of no treaties except with neutral empires, since neutral empires won't come marching through my warp points, colonizing MY planets, etc etc etc.

Re: Diplomatic proposal...what to answer ?
 

The default diplomacy files for all default ai races is extremely unfinished. I've made a mod that at least makes the ai races act like their description. When I was creating my mod, I've noticed that MM just made all the default races act the same way. Be aggressive and break treaties. This method makes sense for some races, but the more peaceful races with descriptions that state that they are peaceful does not make sense at all. I can only hope that the patch that comes out after the upcoming one will definitely deal with this.

Re: Diplomatic proposal...what to answer ?
 

I'm still working out how to use diplomacy well, but I have learned a few things.

Like many strategy games, in SE4 it only really makes sense to trade with empires that are much smaller than you are. If somebody else is equal to you or more powerful, you don't want to give them an additional economic or research bonus.

Also, as I learned in my first game, you don't want to trade with somebody you are eventually going to fight. When my neighbor cancelled the treaty and attacked me I lost a huge chunk of my budget, and my navy just evaporated on the way to the front because I couldn't pay the maintenance costs. Ouch!

On the other hand, if you make a trade treaty with somebody you can get a lot of useful information about him from the "comparisons" button on the race information screens. You could always break the treaty again, assuming you can afford the happiness effects.

If you're worried about the trading partner wandering around your systems simply mine your border warp points. Strangely enough, the AI does not hold it against you if its ships are lost to your mines in peacetime.