Incredible idea! To add a GSM module into old printer, change firmware and start selling it bitcoin forums. Then transmit to a given server the content of suspected prints.
Don't buy a printer on Bitcointak, buy it on Craigslist. That makes a targeted attack much less likely.
By the way, maybe saving seed as a QRcode could be a partial solution for missing parts?
Why not both? I like what a former-trusted-now-scamming paper wallet site did: print the private key twice, one of them upside down, with the QR-code in between. That means you can still recover the key even if you lose a substantial part of the paper.