Crafty businesses are homespun, bespoke businesses that rely on charm and a personal touch. Group buying single-handedly destroys that. Crafters are also very protective of their personal brands and would be very averse to doing anything that might lead to angry/disappointed customers.
So, I don't see this taking off. Have you talked to any crafters about this? Can you allay these types of concerns? And what types of handmade products lend themselves to being made in short timelines and high volumes?