He’s done it, it’s the Output Expander, in two forms:
Add a PB and you’ve got the equivalent of the DigQuad.
And it’s powerful in it’s own right, as @zranger1 has just released code to drive it via Processing: ExpanderVerse: Processing, Output Expanders, Many, many LEDs
I’m a fan of the DigUno and DigQuad boards, and own more than a half dozen. You could argue that they have more safety features, because Quindor is all about the Fuses, for example. (HAHAH, I hadn’t noticed when I started reading that @wizard replied, and said the new version has fuses… so…)