Is there any reason an EC could not be laid out like a 38-40-45 With the high notes at the inside, the low notes at the outside? You could lose the super-high notes, but go down to the low "F" or lower on a 45-button.......
Provided the player didn't mind the sides being mirror rather than parallel, are there other reasons why this wouldn't work? I guess you might not have some of your black-note doubling, but aside from that---Would there be deal-breakers?