Hey, you could save a cool grand-and-a-half by settling for the basic D-7 as opposed to the fully-tricked-out HD-7 ~ why not go for it?

Just kidding of course ;^)

I'd love to give one of these babies a try, although it's hard to imagine having to hit one specific string/pair, the "G," in order to activate the guitar's characteristic sound.

I don't think it would work too well for many of the pieces I currently fingerpick ~ I'd only get that full-octave "doubled" overtone on a random selection of notes. Depending upon the specific piece, the distribution of notes played on the pair of "G" strings (among the many other notes played on the conventionally single strings) may or may not make any kind of musical/logical sense.

I suppose it would work nicely if you treat the "G" as a bass string (alternating bass), downstroking it with the thumb on every 2 and 4. And of course, when you're simply strumming full six-string chords throughout a song, you would certainly achieve a consistent tone featuring that understated little "jangle" in every measure.