Most instruments come in a group of different sizes, each good for a different part in an ensemble and for different purposes. My suggestion is to have the CODA be like this as well. We already have what is basically the "soprano" of the group, and although it's sound and range is nice, more options would open up numerous possibilities. I know there was talk before of maybe manufacturing an "alto" in G, but I would like to see a "tenor" or even a "bass" as well. Granted, the last two might be a bit on the big side to no longer be an EDC flute, but I'd think the option for low tones would be appreciated.
The big question is whether the bisected tone holes could be covered by normal fingers on a larger Coda, or would there have to be keys and pads?
Of course, keys and pads would change the basic character of the instrument, but it's fun to speculate. One of the main advantages of the Boehm concert flute over traditional flutes is that the use of keys and pads makes it possible to avoid most, or all, cross-fingerings. Cross-fingerings are not just awkward but also affect tone quality on a tubular open-end kind of flute. On an ocarina or vessel flute, I don't think cross-fingerings have any effect on tone quality but they are still more awkward than what's possible on keyed instruments.
I think you'd also need bisected tone holes, with keys and pads, for the sharps and flats. I'm picturing a tenor Coda, an octave lower than our Coda, with pads for the basic C scale, like the basic keys of a saxophone. Plus it would have keys for C#, D#, G#, and A#. You might be able to get away with no key for F#. It would have to be big, not only for the low pitch but also to support all that keywork.