Hey! I've been interested on NBTV since quite some time and I've got an idea, maybe it could be interesting for you, guys.
What I'm thinking on is building a receiver/ transmitter that, instead of using a nipkow disk or a mirror drum/ screw it uses an LED or photodiode array.
LEDs didn't exist back in 1926 and it took a long time for they to become the cheap silicon diodes we have today, so this idea is to break down some "classical ideas"
It's wrong say it'll be digital, though. Because I'm thinking opf making the transmission and actual storage on an analog way (Simply using voltage levels, not discrete signals) and the scanning mechanisms could be something like a guy on the early 1900 used for the first television demostration ever. He used a lamps and photocells array and he mechanically switched one or other on and of to transmit the picture cell by cell/ lamp by lamp.
I've done some math and calculated an example resolution in pixels for the NBTVA club standard: 32 x 48. Basically what I've done is take the number of lines and knowing the aspect ratio is 3:2 then I deduced that one unit was 16px, since the shorter side is 2 units and that side in lines is 32. For the side being 3 units I multiplied 16 (one unit) by 3, wich gave me 48. I hope you understood, my english may seem fine but when I have to explain something complicated I go crazy
For the final thing I converted an image of Felix The Cat to that resolution, resulting on a really well accurated reproduction of the original, with no loses at all. Here ar the images: (Notice the one that's been converted is really small, the size it would appear on some nipkow disks!)