Finally, the doors! With a little extra work to make the red paint capable to change colour in it's material instance. Now, to do the decals, a little vfx, and lighting...
AzzaMat - it's quite common to divide a texture into RGB(A) channels and use those for alphas, speculars, decals and whatnot. So what you're doing is perfectly fine.
But do you really need that many textures for that ship? I mean there are lots of places you can use procedural textures. Probably in combination with decals.