The biggest problem for most of these weapons will be making them them into "sturdy" versions without becoming prohibitively expensive and/or absurdly heavy. Some of these I think are easy to see why. The Demon/Soul/Northern Regalia would be insanely heavy for obvious reasons. Storm Ruler too. They'd also share a problem with the "lighter" Blueblood and Penetrating sword.
They'd all need to be forged from one piece of material or the blade would snap off the handle pretty easily. From a realism standpoint, every single one of these weapons you mentioned are exceedingly blade heavy. For a comparison, my uncle knows a guy who forges custom weapons from wrought iron. They're a little heavier than steel but it's a lot cheaper to make, easier and there's no question of them being "sturdy." I have a battle ax that will easily chop wood for instance that's a custom from this guy. I used to have a claymore from the same guy (my brother has it now) that is gigantic by "real weapons" standards. Estimating from the penetrating sword's size it's about the same blade width and thickness. The handles are similar in size (length, diameter, etc.). The handguard on that sword were made from old survival knife blades (looked cool as hell) and might be a little lighter than the decorative penetrating sword's. However, the blade is only about two thirds of the length. That sword clocked in at 10lbs which seems light but is actually crazy heavy. My battle ax I mentioned has a very wide blade, some cut outs to make it light enough to use and is still as heavy as a small splitting maul (15lbs). A splitting maul for battle purposes for a normal human has a swing speed (and more important a recovery speed) about equal to Grant or Smough's Hammer's in my experience. Basically, it's not for most people. My battle ax is usable for me primarily because of the shortened handle compared to a maul meaning I can use improved technique to maintain momentum bringing it back around.
Anyway, long explanation aside, the penetrating sword is one of the lightest you mention and that would be well over the 10lbs mark, mostly in the blade. My claymore had the benefit of a very large weld point between two very strong pieces (blade and handle) and a poor swing would still give the impression the blade could snap off if mishandled.
So basically, the lighter straight swords (penetrating and blueblood) would be possible but extremely heavy and require a lot of care in building. AKA....."expensive as hell." The alternative would be to sacrifice material quality and sturdiness. Now back to the beginning and think of how heavy a solid chunk of steel or iron would be with say, Northern Regalia. Similar length to Blueblood but much wider. Much thicker. While possible to build, you're not hanging that on my wall.
Makoto is the most reasonable and could likely be produced relatively cheaply and still be sturdy. It's a little long for the sword type but it's not actually crazy. The thinner blade style helps with the blade's weight. That type of sword is more often manufactured as a single piece of steel as well with the handle being maybe just a little thinner to accommodate the grip. The tricky part there would be finding the right type of steel to give it the right look of age without actually rusting. The intricacies of the notches on the sword would be a big factor too. A cheaper manufacturer could still make the notches but they'd look cheap. A careful manufacturer could make them look awesome. In all instances of that sword though it might be fun to swing around but the blade will be fragile. Notches are never a good thing.
Another fun fact just to toss in there. My brother sometimes has the ability to obtain scrap steel at work. He made a pair of claymores from 1/2" steel and about the size I described of the wrought iron one earlier. That one has about 1/4" or thereabouts thickness on the blade. The Blueblood sword would be similar size to what he made (thickness, width of blade is closer to penetrating sword). He notched the blade for looks. There are hole drilled to reduce weight. They are nowhere near the size of Storm Ruler or the Brandts let alone Northern Regalia. You might look at what he made and say to yourself, "those are interesting weapons." But I'll be absolutely clear. These are not weapons. Not for a human anyway. If you're strong you might get one swing in that will be telegraphed and you will be killed before you can recover with them.
Last edited by skarekrow13 on Fri Jul 26, 2013 12:26 pm; edited 1 time in total