This problem will probably require a lot of development effort to deal with. I believe that the graphics subsystem is generally set to use 1 pixel width lines, so as the pixels get smaller, the lines they are made of become less visible. Maybe the solution can come from the card maker as a custom control for stroked lines.
Adobe dealt with a similar problem. In PDFs lines are given widths, but when zoomed out, those widths can be smaller than 1 pixel. In grayscale displays Adobe would use aliasing to approximate the lines by changing the pixel color to represent the proportion of line; if a black line would cover 1/2 the pixel, the pixel would be 50% gray. However, if the lines were thin enough they would essentially vanish, so Adobe added a setting to round up to the nearest pixel width, so even very thin lines would be 1 pixel wide, and thus generally more legible.
The PTC problem is their lines don't typically have a real width associated with them, and even if they did, they will eventually run into the same problem Adobe when 1 pixel is too small.
The best answer is for Microsoft to use SVG for it's interface elements and build in scaling to the screen size so that icon sizes are invariant without having to build them as bitmaps at different sizes. PTC could make their own subsystem as well, but as I started with - it will take a lot of development.
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