From what I've seen (and heard) of Civ IV, I'm not planning on buying the game anyways. Hell, one of the reasons I got Civ III is because of the realative ease of modding..... I figure if worse comes to worst, just download GMAX (Freeware version of 3D studio max that has all the features of the main program, but you can only save/export the files as whatever game format your plugins support, i.e. Half-Life .mdl, etc) and use that to make the units for Civ IV
Anyways, I'm assuming you have the newest version of Blender, because I have an older version and due to interface bugs (menus closing when you try to click on them with the mouse, etc), I never use the program for anything but making some complex design/misc parts for my Bryce stuff (I import the DXF files and re-size/re-texture them as needed. The Stars on my Tesla tank were done using Blender). Once I get my high-speed wireless internet set up, I'll be downloading the latest verion of Blender just to see what it's like. If I like it, I'll be using it to make more complex models than I'd normally create in Bryce, Import the parts and animate them in Bryce (I'm sorry, but the only program that I've ever worked with that could hold a candle to Bryce in terms of Textures and lighting was 3D Studio Max). Then again, I'm planning on getting Shade 7 (I was impressed with what I saw of the program when I first came accross it in Japan, now that it's in English and only $300, I'm tempted to buy it), so I don't know....