Simple but effective.
i only would add some insulation to the threaded rods. I used some clear tubing from a pet store (used for air pumps) but some garden hose or watertube from a RV store will do just as fine.
If somehow the cells start moving, the plastic wrap isnt damaged by the threads.
For insulation between the cells I use the Ikea Finfordela chopping boards. Slightly more stiff than the ones you're showing, but I think they also are a little stronger. And they are cheap, $1.49 for 2 pieces 11x14"
But.. no threads or terminals on your cells. that's going to be a bigger challenge than the cell pack itself. Good luck!