Alternative lateral-thinking options like that are a superb idea ! I'm all for alternative options and different ways of looking at a problem. :)

Does anybody have recommendations (and links) for stuff that does that? (Most modelling software I guess...)

(The comment also reminds me that double-sided faces/meshes have their own problems. And what exactly do people mean when they talk about double-sided meshes? I know in Blender 2.49b that if you have a 4-vertex 1-face plane with the 'double-sided' button selected and you export it you get an OBJ with a single face. So is the double-sided/single-sided distinction actually in the software, not in the OBJ?)

I assume that you're talking about something that would convert an OBJ file like this simple 1-face 4-vertex example...

v 1.000000 -0.000000 -1.000000
v 1.000000 0.000000 1.000000
v -1.000000 0.000000 1.000000
v -1.000000 -0.000000 -1.000000
f 1 4 3 2

...to this (if it simply creates an additional face with an inverted normal using the same vertices)...

v 1.000000 -0.000000 -1.000000
v 1.000000 0.000000 1.000000
v -1.000000 0.000000 1.000000
v -1.000000 -0.000000 -1.000000
f 1 4 3 2
f 1 2 3 4 ...or this (if it extrudes the face to give it some thickness - normals may be wrong on this one)...

v 1.000000 -0.000000 -1.000000
v 1.000000 0.000000 1.000000
v -1.000000 0.000000 1.000000
v -1.000000 -0.000000 -1.000000
v -1.000000 0.100000 -1.000000
v -1.000000 0.100000 1.000000
v 1.000000 0.100000 1.000000
v 1.000000 0.100000 -1.000000
f 1 4 3 2
f 3 4 5 6
f 4 1 8 5
f 1 2 7 8
f 2 3 6 7
f 6 7 8 5

I know that the middle version (with the two faces, which I think is what most people would call "double-sided') causes problems in Poser Firefly (random black rectangular patches on the face).

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The 3Dcheapskate (also available in DAZ and HiveWire3D flavours) occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.