Something like this? The heavy stagger is great, 42 keys is almost perfect, but the thumb placement is – for me – horrible. Having to move my thumb to practically under my palm is just terrible ergonomics.
This thumb layout reminds me more of the ErgoDox variants, and is far better placement. Is there a layout close to this?
Apart of Kyria, Hillside keyboards, Birdy44, and KLOR are similar to what you picture here. Maybe even Porcupine, but that’s a key short per side.