Ideally, for debris, you could come up with a new set of uvws for a new debris map, then use uvw channels to bake from old uv's (channel1) to the new ones (channel2). What this does is that it allows you to have a new map with efficient uvw usage for debris, while matching the hull perfectly. All that would be left would be to dirty the new baked maps up in photoshop, so you could simulate burnt edges, etc. I wrote a tutorial on how to do this some time ago, it's not perfect and I'd need to revise it a bit before releasing it to the public, but if you're interested I could probably dig it up.