Someone at work asked me the following question, that I was only able to answer in the negative. Maybe someone else knows differently.
He wondered whether there exists a set of MX-compatible keycaps that are backlight friendly (i.e. let the backlight show through transparent legends, like the OEM Ducky Shine keycaps), that have primary Roman legends (i.e. A-Z in US ANSI layout), and that also have Cyrillic legends (like Ivan's recent GB).
Another requirement: black keycaps.
Yet another requirement (but perhaps optional): that the backlight shows through both primary and secondary (Roman and Cyrillic) legends.
Has anyone even heard of such keycaps?