I honestly have no idea how any of that would work. Changing a xml value is easy enough. Scripting in new functions or knowing what functions and commands to use is past my little bit of skill. I can find pieces from xml's and combine them and then edit them into something that works for whatever simple thing it is I'm trying to do most of the time, but I think we'd need a local xml Wizard for this one.

Finding people good with code who want to help for fun can be as hard as finding "Where's Waldo" when he's hiding in a barber pole factory next to a candy cane warehouse.

Yeah, I know about the starbase spacing thing, I'd just rather leave that alone and make it so that even if a world happens to be within the AoE of two or more economic starbases it'll only get the bonus from one of them. The only thing stacking economic stations adds to the game is even more constructor spam in my opinion, and given that the bonuses from economic stations tend to be more worthwhile than whatever you can do with the one or two resources you might be preventing yourself from acquiring by building the 'ideal' circle of starbases around each of your planets, I tend to think the game would be improved without the stacking.

How do the materials and surfaces work?

Guessing - the "FactionNameTexture_A_Data.dds" is like a material properties ID or some such, but not sure, but I think is like a specular amount control not unlike a specular map in SoaSE.

            - the "FactionNameTexture_A_Diffuse.dds" is what is says, diffuse.

            - the "FactionNameTexture_A_Lean1.dds" is like and inverted normal map with the red channel copied and inverted to the alpha. Guessing it works something like normal map.

            - the "FactionNameTexture_A_Lean2.dds" seams like again normal map data but with the flat surfaces removed. Perhaps is like a coloured curvature map but really don't know.

            - the "FactionNameTexture_A_Light.dds" seams to be an emissivity map for the ship windows and lights.

            - the "FactionNameTexture_A_Normal.dds" is what it says, a normal map.

There's probably no reason to make variations of these for custom faction ship styles other than the diffuse and light map though I guess.

Then there is Surfaces, which maybe there could be variations made for custom faction ship styles.

Again Guessing - the "OverlayTexture_##.dds" seams to be a diffuse with red and blue channels filled white. Not sure how the alpha is derived. I'm guessing this provides some shading overlay, similar to what the lean1 map does for the materials does.

                    - the "OverlayTexture_##_Lean.dds" seams to be similar but different to the Lean2 map of materials. Looks like a normal map with the blue channel removed or made black. No alpha. Again, I guess this provides some shading overlay.

                    - the "OverlayTexture_##_Normal.dds" is what it says, a normal map.

I have tried making a custom surface, but it made the ships appear completely black. Maybe it is how I've tried to replicate the texture maps, but also and I think more likely, its how I referenced the maps with the xml. and they are showing black because the texture maps are not being read at all.

How I have this set up is a Copy of the "GC3SurfaceDefs.xml" renamed it and put it into my mods Core folder. Deleted all entries except 1 and renamed it and put reference to my textures for it that I had put in the Gfx/Models/Ships/Textures folder of my mod. Then made the relevant edit to the FactionDefs.xml surfaces line. The surface shows up in game and you can select it in the in - game custom faction editor but it is showing completely black. So I'm guessing that I'm missing something in the xml. but I guess it could be the textures.

Anyway maybe someone could explain a bit more of what's required.

Thanks.

Edit: so I have got rid of the black, oops my bad  but the surface still doesn't show on the ships and just stays as the last selected surface eg. surface 19 or surface 1. 

Oh yes I have read Derek's post several times and I'm comfortable with what he's explained with the GC3_MaterialDefs.xml. To be honest I'm quite lost as to what's going on with material defs. Just was thinking if there was something to base it all off you could know which direction your going with things more.

2. Tech costs are defined in tech tree XMLs as an integer, without any possible modifiers. You could have every tech decrease the amount of research points that the faction can do. But you already said you don't want to tamper with colony output.

3. There are two modifiers, Flat and Multiplier, both can be signed decimal numbers(+0.1,-0.1):
Still not sure how exactly Multiplier works, as I have tried to have it at zero, which seems to make no changes, when I want to have the final parameter to be always zero.