hope they will fix the issues for compatible with WinVista64.
Unlikely, based on this:
Only Window 7 and 8 will be officially supported.
Still, with GalCiv 3 on the horizon, I really wonder if it is a good idea to begin working on such a big mod for GalCiv 2. Even under the best of circumstances, by the time you're finished, GalCiv 3 has either been released or is close to release.
Then there are the limitations of GalCiv 2 to consider. A lot of things are either hardcoded (like most random events, all Mega Events, the amount of races you can play against, how alignment works, etc.) or limited due to bugs (like the amount of starbase modules the AI can use or how upgrading 1pp improvements works).
Based on my look through the files, GalCiv 3 is already much more moddable than GalCiv 2. Recreating the map of the Alpha Quadrant to scale, and adding all of the races? Should be no problem once the game-engine is fully optimised. Frogboy already said, that he could imagine 100+ civs in a large enough galaxy. So, no more limit as to how many races you can play against. Changing all events to take the Prime Directive into account? Totally possible. Adding cloaking-devices for ships? They are already in the game-files, but I have no idea how they work (or even if they make it into the final game).
This, plus all the new additions (like nebulae, black holes, stellar resources (which are required for advanced ship-components), planetary traits, open/closed borders, etc.), makes GalCiv 3 a much better base for a Star Trek total conversion. Well, or any other sci-fi total conversion for that matter.
If you still want to use GalCiv 2 for the mod, then I can offer to answer any questions that come up. That's all however. I've finished my mod (which took almost six years), and I have no intentions to start working on another one.