The AI trades so badly that one can easily outperform it and win all too easily. Examples that should be fixed:
1) You can trade in a substantial part of an AI-opponent fleet against some techs (and maybe some minor ressources or quite remote and userul starbases). Thereby the AI looses all its defense and the players fleet is greatly and quickly strengthened so much that the AI can be crushed within a few turns.
2) One can easily get the alone tech leader by simply trading techs round the different AI in the following sense: trade tech a, b ,c against d, e with AI no 1. Trade some of your a-e techs with AI no 2 to get also tech f, g and so on and so on. Although usually you have to give each single AI opponent a little more than you get, but in the end you have gathered (almost) all currently researched techs and each single AI has only received a few techs.
Proposed solution:
It has to be ensured that the AI behaves more like a good human player, i.e. it mustnt trade with the player if the player has a greater advantage than the AI player itself. An algorithm that only compares e.g. manufacturing costs or research points from the two trade parties and then says 'yes, lets trade' if the AI get eg 10% more in a certain trade is not suitable. Additional factors/penalties have to be introduced within the trade algorithm if the player gets e.g. very good ships which can be used to invade planet and thus are much, much more valuable than just the manufacturing points of the ships. Or the AI demands kind of a non-invasion agreement for the next 50-100 turns (after which the traded ships are outdated and thus not dangerous for him anymore) if he trades ships against somerhing.
In case 2) above, the AI has to act smarter, too. Either the AI also plays the same trading game with the other AI-opponents and thus soon everybody has (almost) each researched tech or it has to have a substantial advantage from the traded-in techs. Military techs seem to be 'valued' a little more by the AI, which also doesnt really make sense because there are a lot of non-military techs that give much bigger advantages than e.g. the next best laser tech.
Actually, I am not quite sure if the AI being used is really able to 'plan and play meaningfully and really in an intelligent way'. If the algorithms are not able to 'judge well' about the benefits of a certain tech trade, this trade option should better be eliminated because the AI is playing 'suicidely' currently.