Good stuff.
I've been trying to get a micro punch and die set, but the only one that was available in the UK was the Waldron set, now discontinued. The Micro Mark set can be had from the US, but the cost of shipping, and then Import Duty, is prohibitive.
Printing the decals on white decal paper can work as a reverse image (i.e. black background and 'clear' lettering, or coloured lettering if needed), and I have done it in the past, in 1/48th scale, for a placard that measured about 5 x 3 mm. However, the resolution is not brilliant, due to the nature of inkjet, or even laser printer toner. It was passable enough for that particular need, but the lettering was not sharp, and was partly indecipherable.
It may work better reverse printing onto clear decal sheet - black background, clear letters - then placing the decal over a white painted surface, to give white lettering on a black background.