1. I don't like the idea of wielding a claymore with one hand.
2. You can wield a one handed sword with both hands? That's awesome. That's... Wow... Um... I just got a woody.
Unless i missed the sarcasm..
There s a diference beetween carrying a 2 handed weapon with 2 hands, you can add strenght, but its unpratical.
That why the hand an a half sword was created, sometimes called bastard, because it reside beetween the 1 handed and the 2 handed.
In medieval times shields where made of wood and painted, few where iron clad, and almost none had even a metallic sheet.
So after 2 relatively strong people would bash each other or in a long fight in a clash the shield would go to pieces and handling extra strenght and speed with an adequate place to place the second hand could make all the diference between being dead meat, mauled or get out safe and victorious.
Even if the bastard sword wasn t that popular it had logical reason to exist.
Weilding a 2 handed weapon with one hand lossing speed, strenght, control and balace is signing a suicide recipe in the middle of a battle or a duel.