A forward swept wing was indeed unusual at that time, although not actually unique.
But even though it is known that Junkers knew they had to locate engines (ie weight) along the wing to counter the twisting effect FSW's encounter (hence the triple engine configuration the real production types were supposed to have) it is pretty much accepted these days that you need much stronger materials & FBW computers (not to mention computers in design to make the necessary stress calculations) for FSW work safely & properly.