09-06-2017, 05:39 PM
I wonder if modules like these could be used? They come in various configurations, although I don't know how easy it would be to get double width (or double height) keycaps to fit.
http://www.ebay.com/itm/1pc-of-5x4-KEY-S...1864414707
http://www.ebay.com/itm/1pc-of-5x4-KEY-S...1864414707