I don't even know if this is going to be a big or a tiny ask, and I don't know if I'm going to end up with this beautiful product at all, but just in case it's going to be trivial to do so, could you add an option or extra keycaps to have Caps Lock key physically engraved as "Control"? IIUC the ctrl-caps swap itself isn't so rare, but actual keycaps engraved as such seem to be relatively rare.

It's apparently a UNIX thing, and old Apple, NeXT, some of DEC, Sun, HP UNIX, Sony NEWS, even IBM XT, many of modern Mac JIS, etc. seem to/did/do have the legends for that key as "Control", "CTRL", or "Ctrl". I think that adds even more to the cool factor.