Can you make a CPU out of electronic components drawn by hand on paper?
If the gain of a single inverter is less than unity, then it will not be possible to combine any significant number of gates together to build a larger circuit. The signal levels will just peter out.
To be viable, a circuit for building logic needs to have output signals that are compatible with the input of the next gate. At first glance, your inverter has a 0-12 V input swing, but a 6-15 V output swing. The voltage gain is 0.75, and there's also a significant offset.
I found a copy of the paper here. In it, they provide the following graph of input vs. output voltage. It turns out that your notation of an output-low voltage of 6 V is overly optimistic — it only gets down to about 7V, achieved when VGS exceeds about 40 V! Even if you drove your first gate with the full 0 to 40 V swing, its output would only go from 13 down to 7 V. If you then try to drive a second gate with this signal, the output of that gate wouldn't budge at all!
Furthermore, with the very high impedances involved, the clock speed would have to be extremely slow — probably on the order of a few Hz. Which would be fine for a demo, but not much else.
Paper transistors or not, a discrete transistor CPU can be made to be a reasonable size.
On 15 November 2006, the 35th anniversary of the 4004, Intel celebrated by releasing the chip's schematics, mask works, and user manual.[39] A fully functional 41 × 58 cm,[40] 130× scale replica of the Intel 4004 was built using discrete transistors and put on display in 2006 at the Intel Museum in Santa Clara, California
Though not done with paper transistors. That particular display does not even come close to taking up a room.
http://intel4004.com/current_intel_museum.htm
Your best bet to fabricate the paper transistor patterns would be to get a few cheap black and white ink-jet printers (either with a tank or cartridge) and then replace the normal ink with your new ink. Each printer would be used for a different fabrication step and have a specific ink.
Break down the fabrication process into a set of steps involving laying down a specific pattern in only one kind of ink per step. And then run the paper through the appropriate printer with the pattern for that step.
Your only major problem will be aligning the paper between each step. That is solved by making the features large enough to account for the positional tolerances of the printers.
For the circuit traces you can use any number of commercially available conductive inks (usually silver filled).
Or make your own.
https://spectrum.ieee.org/geek-life/hands-on/how-to-brew-your-own-conductive-ink
To handle crossing routes in the layout you can use any insulating ink and print the insulator at the points where you wish to cross another trace.
It might be worth it to go as far as making a whole layer of transistors printing a full page insulating layer (minus any connection points that go between layers) and then print the next layer right on top of the insulator ink. In this way you could get multiple layers on one sheet of paper.
I have helped people build science fair projects with a paper circuits, and the cool thing was that the circuit diagram and the circuit were one in the same, so everybody could understand what was going on. We used pencil lines for resistors, and it was nice to be able to adjust resistance values with just pencils and erasers. We also found that you can buy aluminum foil tape with a conductive adhesive, which provides a good, low impedance connection. However we didn't try to make transistors from scratch. Looking at the Wikipedia article "Field-effect transistor", it seemed like building a FET was fraught with difficulty. We ended up just incorporating commercial transistors into the projects. I also used to build experimental computer circuits. The main problem with computer circuits was just the sheer number of components required. I would come up with what I thought was a really simple design, and I ended up having to interconnect hundreds of components. So I never tried to build digital circuits on paper.