Instead of one large channel throughout the whole print, why not multiple small 2-4 layer bridges?

I had the same thought -- with a checkerboard pattern of 1:1:2 "brick" voids where each brick would be surrounded by bricks of a differing offset, one could conceivably calibrate the injection step and the print might have less propensity to cleave along xy planes. But, given the complexity of that calibration (and need for a high-flow head) I'd rather use the brick infill available today.