I'm not sold on the typograhy for the numbers, it seems a bit overdone.
The rotary encoder seems a bit pointless, I wouldn't know what to use it for other then volume perhaps?
Could the aluminium base be replaced with more of the recycled plastics? If you are going for sustainable, that seems more sustainable then milling one of the more energy intensive materials we have, even if it recyclable. If I spend a lot on such a nice keyboard, I would hope it lasts long enough that recyclability is not the most significant. ( Disclaimer: that is 100% based on assumptions about materials etc).