I've accidentally cut myself while doing sugar work! That stuff is almost as sharp as glass. But it is even more brittle.
Most people are familiar with flint napping, again incredible sharp, but easily broken against steel armors.
Even copper, brass, bronze can hold an edge long enough to cut you.
IMO, all of these could be made enchanted weapons. Now, the breakage numbers would be incredible, you may just get one good roll of the dice on an attack.
I believe the AlcCo says that weapons have to be better than average, but I'll look it up. I had thought that's how it was normally played.. but it's great if I'm wrong.
My issue with having a requirement of quality before enchantment....
Icarus. I like to think that with an awesome roll, extreme knowledge in the subject matter and enough PP/spells, you could build wings out of feathers and wax.
As for variable bonuses, you could have a mighty fine quality weapon, but it doesn't hit "magic" creatures or crit on the magic weapon crit table unless you invoke it's name, or "By the power of Greyskull", or something. Then, the magic bonus would be used.. for that round, a few rounds, that combat.. whichever.
Just a suggestion on how to have variable bonuses.