Just something that might be of interest .. an something I dabbled in as I used to be inolved in point of sale systems.. the keyboards used on these are bloody brilliant controllers for dj /production systems and robust as hell as they are designed to live in bars and heavy hammering from cash register staff!
I've attached a sample image of a way overpriced tipro one ($500!), but you can pick similar up from china for under $100 (check alibaba) with the software for creating the Macros.
Most have multiple layers and you can buy keycaps to make 2x2 large keys
Theres a few gamer keyboards that would do the trick nicely as well but most don't have that many layers or the durability (and do have the price!)
Considering you get 108 x 4 layers programmable buttons .. not bad huh
Oh forgot to mention you can internally daisy chain the one below together with other same model
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