Gehazi- I think it depends on the individual sword-a lot of older (especially tribal blades frow whatever culture) are constructed from a soft body with a little strip of hardenable steel for the edge (since edge quality steel was much more labor intensive) [incidentally I'm pretty sure this is why Filipino stuff that's old is chisel ground]. Some of the body steel can be really, really soft. Steel wool will definately scratch the softer stuff. And steel wool will eventually start to wear away the patina on anything. My older blades either get just the oily rag treatment, or cleaned completely and re-etched, depending on the blade, its value and/or rarity, and how messed up it is to begin with. Everything you've put up pics of, I would just oil, maybe scratch down active rust with a penny and oil to stop it from getting deeper, and enjoy them.
Incidentally, as to the original subject of this post- It wouldn't be too hard to make a wooden scabbard with panels of brass and bone inlaid into the front.