The 12 tones for the sympathetic strings I should have thought, although I see the Thomann page recommends a Dsus4 chord.
From a commercial POV the trouble is there's so much hardware it would all get awfully expensive. Each sympathetic string needs a tuner of some sort, if only piano/dulcimer/harp style key ones, you need pickups, and in a solid body as the link mentions there is an issue with getting the sympathetic strings to move enough. Nothing impossible, but boy I bet it would all add up to a rather expensive kit.
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