Can you refine what you mean by "the limit of perfect technology"? If you expect atomic tweezers, you're probably right. If you expect superpowered but still annoying analogues of current methods for manipulating individual atoms, you're probably wrong. Nanotech is surprisingly hard - it looks less like surgery with a knife you made with a rock and more like using the rock to pound on the knife's handle during surgery. (But I'm an amateur.)