Lumpy, speaking from experience, it’s not entirely bad to have the weight of the helmet on your head. I have found that a heavier helmet keeps my head from rocking as much if I get hit, thereby reducing the chances of whiplash type injuries. Also there were gauntlets made in period that could be pin locked around a weapon, so that it would not be dropped…not quite a “vice grip” but then, a vice grip would also cause a drop in the mobility of the weapon.
As for the weightbearing framework, I’ve actually seen this done. The main problem with it was that, while the suit wasn’t too heavy to wear, it was a major pain to move in. With a properly fitted medieval harness, the armour’s weight is fairly evenly distributed over the body, tied in various places to make it seem lighter than it is…so though your body is bearing the full weight of the harness, each part of your body bears a little of it, and it makes it feel much less heavy, and allows you to move easily. With the frame supported suit I have seen, the legs and back had to do a tremendous amount of extra work to move the suit than they would have if it had been properly pointed to the person’s body.
Tristan, what do you fight in now? I am working on a “as close to accurate as SCA rules will allow” suit currently; late 15th Century Spanish harness, with floating steel arms, pointed 3/4 legs, and fitted brigandine. Thus far, it is coming out really nicely, and looks to be a vast improvement over my first suit of pickle barrel plastic and aluminum…