I would think that a progressive range from high to low without a big step in the middle has some real advantages. Relatively large steps between gears may be objectionable to some but OK for others.

I would guess that some or all of the big tandem builders would have considered this (and maybe rejected it for this very reason).

Not sure how Sram does a 10 tooth cog. 11 teeth was the smallest standard for a long time.