Hi! There's quite a lot of modding features that are nearly completely undocumented, due to lack of interest :) You can start by checking this out:
http://blog.galimulator.com/2-uncategorised/2-maps
If you want to set up a scenario, you can also use the undocumented feature to set up maps with pre-designed empires, like this:
empire.1=Snod Empire;10%,1,0.5,1;1,0.5;
Will create the Snod Empire for you, owning 10% of the galaxy, with color = RGB(1,0.5,1) (I guess ... light purple?) and positioned at (1,0.5), which I think is around upper right corner.
If you want to play around with this stuff, let me know, I'd be happy to include well designed scenarios in the game.
Oh and you *can* set the government type when making a new nation, starting in the new beta.