Whatever the solution, it'd have to account for:
* Poor weather
* Thieves
* Ingress of fumes
At a guess, it'd have to have a custom track built for top and bottom rails, with a framework around the glass that incorporated a rubber wiper that provided a seal against weather and exhaust fumes, and some sort of lock on the frame (even if it were just a lever apparatus on the inside).
Page 41 of Nissan's workshop manual details the rear window - according to it, the window has a rubber seal placed around the glass and it is then glued into place with a urethane adhesive and left to sit for 24 hours while it cures. Leaks are also treated with this same urethane adhesive.
Being glued in, it doesn't allow for much "meat". You'd end up with a thick overhang if you installed a rail system for sliding windows. You've only 15mm of overhang of glass over the metal lip and judging by the images, you've got about 10mm tops in thickness to play with. With 2 sheets of 4mm safety glass, you've got 2mm of framework left to play with and that doesn't allow for the unit to be fixed to the vehicle.
On the inside, clearances at the top are worse - the roof panel comes right down to the edge where the glass is glued. The top of the seat should hide the bottom part of the window from casual view and hopefully won't interfere with the window - the D22 I took for a drive was so squeezy between the seat and back wall when I tried to fit the baby capsule so we could cart the grandson around that it didn't even like the safety harness going in.
Would it be possible to install a tinted perspex window and have a sliding panel within that?