This is a fun headline, but we’re still far from useful functionality in this direction. 3D printers can barely even print circuit boards except for a few exotic prototypes of trivial complexity at hilariously low resolution. More impressive than the progress so far in the DIY community is Xerox’s silver printed circuits. Various conductive inks have been developed before and nothing came of them in terms of commercialization. Development by Xerox started in late 2009, it’s been over a year now and no news yet.
In terms of strength, the products of 3D printers are weak and can easily be pulled apart with your bare hands. If you want a strong product you still have to go to the machine shop or foundry.
Interesting proposal solicitation, however it is worth remembering that military commanders have been making breathless requests for futuristic technologies since time immemorial. There will be no “semi-autonomous breeding robots with built-in 3D printers” of practical battlefield value until at least 2025. However, this is the sort of thing a superintelligence could build millions of to do its bidding.