As some people know, you can already mod Galactic Civilizations II quite heavily. We have a basic modding guide already up. The coolest mods are going probably going to involve the ship stuff. I've already seen people putting in high-polygon models that look really cool. All you have to do is load up Maya or 3D Studio, make your ship model or part or whatever and export it as a .X. Hard points are just dummy nodes that we did with 3D Studio. There's no polygon limit so you can go nuts. Then in the \data\english\gc2types.xml file you just put in your own stuff.
Of course, when it comes to sharing your mods we need something more robust. So this is a preview of what should be part of v1.1. We want to explicitly support total conversion mods easily.
1.1 will create a \Mods folder on install and provide an example mod that we'll make. The Mods folder is essentially a mirror of the GalCiv2 directory. For example:
and so forth.
In the root of the actual mod folder (using Babylon5 as an example since JMS has tended to be more supportive of mods and fan content over the years) you would have a mod.xml file that will provide a description of the mod and various notices/permissions that the mod author may have needed to obtain.
There will also be a \Generic directory which will simply be a catch-all for all the mods you get from here and elsewhere. You can just dump your stuff in that directory and the game will use it. The game won't care about the file names of the XML files. It will only be looking at the key names in the XML files.
In the Games Options window, there will be a Mods button that when pressed will bring up a dialog asking you which set of mods you want to use. Based on what you select, it'll add those ships, screens, data, etc. in and replace the included ones when applicable.
We hope to have v1.1 out by either the end of this month or early next month. We're currently working on getting the demo out the door.
Mods will be available in the library section, though be aware that we're clamping down on copyrighted material. Don't upload to us other people's work unless you have permission.