I don't believe there are any serious technical obstacles to providing a graphical installer in something like an initramfs environment. Many distros do provide graphical installation mechanisms using PXE, which loads the kernel and installer-initramfs over the network (and is similar in the sense that it won't touch local storage unless you tell it to)

I don't have a way to quickly around to check, but I thought the arch install media used squashfs? In which case I wouldn't have thought it was safe to blow away the backing store.