Why doesn't Starfleet just employ more Borg cubes when fighting Borg?

Seriously, with the devastating defeat to the Borg and the Borg uni-matrix, you would have thought that Voyager would have took home some extras cubes, or at least Spheres or Probes as souvenirs. The Borg wouldn’t of noticed that those ships weren’t Borg, and Starfleet would have gotten some killer Victory Royales against...