Is there any mods that improve the AI and the animations for the Xenos?
No. You can do some tweaks for the AI in the .inis but other than that no. Its not even worth looking for those tweaks. As far as I know some of the lines and/or most of them revert to their original states after you start the game (even with read-only check somehow).
Yea all the good stuff is wrapped up in unreal editor files which are under 2 layers of compression. You can totally unpack them to see all the the goodies inside but for some reason nobody has made a program to re-pack them after they have been modified.
Now a nice thing to note is that you CAN still load partially unpacked files with the game and you can get around file size checks which means if someone makes a repacking tool then it might be possible to load modified stuff like AI and meshes and animations n stuff back into use. Why only half the tool exists... i dunno, it makes no sense to me.
All GBX would have to do is allow people to load unpacked folders...
Hopefully Gearbox patches this sh**... I'm still really upset about what happened to this game.