Here's another crazy idea... how about taking the rotation spindle for a Phototherm, (the piece that looks like this: http://www.phototherm.com/interctr/pvw2.gif ) and somehow fitting it to the guts of a Nikor 4x5 tank? What is the diameter of the hole in the middle of the nikor 4x5 reel? I wonder if the phototherm spindle could be made smaller diameter (it seems like it's a little wide, from just eyeballing the pictures). That might allow 12 sheets of 4x5 per run of the phototherm, assuming chemical coverage was high enough... ?
You couldn't rotate 12 sheets. They wouldn't stay in the reel. Too much dynamic drag on the film edge.