F-One had the "Slider" I think it was called. It had an inflatable LE, but was foil the rest. Semi supported by a bridle.
There was also the Vado Retro Arch VRI. It was a real C-kite shape with 4 lines to the tips, no bridle, but was a foil with an inflatable LE.
I have also always been interested in putting an inflatable bladder down the middle of a flysurfer kite to see what would happen. A bit more rigidity to the flysurfer kite would be interesting!