The Thumbwing is the idea of a mostly thumb-operated mechanical 30% keyboard which you hold like a gamepad and which has the modifier keys on the back side as well as some shoulder and belly keys.
The idea came up after holding an Alpha28 like a gamepad with both hands and typing with the thumbs.
Red are backside keys, yellow are shoulder and belly keys. The belly keys are probably mounted in the same plate as the normal keys, just with keycaps mounted 180° turned, so that they have the surface showing more towards the belly. The same might work with the shoulder keys.
The partially covered remainders are the standard columnar staggered rows 2 to 4 taken from an Atreus (as it was available as preset in KLE), but with 30° turned instead of just 10°.
The idea is that at least the index fingers are not resting on the backside but on the keyboard’s shoulders to keep the keyboard from slipping out of your hands. (I should probably move the shoulder keys more to the outer edges, my index fingers aren’t that long.)
Backside keys at least should be doable in both, Kailh Choc low profile switches as well as in classic Cherry MX compatible switches.
The idea of this keyboard came up during the discussion in the Concepts for Sub-30% Key and Layer Layouts? thread on Keebtalk.