Awesome. What 3D editor you have is of no consequence. Blender will do just fine, you just need it to see the texture on the model, to have some feedback. But in what form the model will be presented is irrelevant to the work on the texture.
Now the texture work preferably would be compatible, but doesn't necessary have to. But there are other things, like normal maps, that will require some creative workarounds or task splitting, if you won't have Photoshop. See, many of us use this Photoshop plugin called NDo, that is an amazing thing for drawing the normal maps with in the Photoshop. And the normal maps then are used for the fake-ish ambient occlusion layer that you can use for basic shading of your texture. it does a lot of work for you. If you have a Photoshop CS6 and newer, you can even use the 3D texturing with DDO plugin Unifin presented in his video.
If you'll stick with the Gimp, then either I'll give you the basic texture after I'll make the whole normal map. Or you'll make the armor lines and I turn them into normal map and send the thing back to you.
Corel Draw isn't relevant here.