Keet,
First of all thank you for the prompt, comprehensive and comprehensible reply! Suggestion 2 is it. You may stop reading here. The rest is only my afterthoughts for the interested.
#3 is the easiest to make, as I model the geometry in FreeCAD. The number of arrayed holes can even be parametric there, thus controlled by the respective variant of my part. But I have only a core i5 and 8 GB RAM
, no Cray 
#1 is what I had figured myself soon after I had posted. But wouldn't the texture image be huge? My largest part would require 4 MPx for distinguishable holes, and the project may contain many shelves. What is most expensive? - Mapped texels while rendering (i.e. after repeating the texture tile), or actually rendered texels (renderer might skip obscured or simplify too far texels), or source pixels loaded from the texture's origin?
My #1.5: The ideal aspect ratio of the tile is 1/√3 in my case; 15/26 comes close enough - indeed the Px size of my texture. Now, I might make a "meta-"tile of 26 x 15 base tiles, yielding a 390 x 390 Px square which suits SH3D.
#2 made me smack my forehead for why I haven't found it myself. The definition of the target area is already defined in the CAD model by a "stencil". All it takes is replacing that by an array of stencils. This costs only 2 triangles per hole pair (in contrast to 56 in #3, circles already simplified to hexagons).
Thanks for that really new approach!
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Cheers - Joe //
