Conductor-Composer-Pianist Extraordinaire Daniel Barenboim has collaborated with Belgian instrument-maker Chris Maene to produce an interesting straight-strung grand piano. He was inspired to do so after playing Franz Liszt's imposing concert grand piano, which is straight strung.
Barenboim says that the new piano has "more transparency, more clarity." He probably means that the piano sounds more pure... from the bench. I doubt very seriously that it makes any difference at all by the time you're at a typical audience's distance; a spectrum should bear that out. The performer sits in the near-field, so to speak, of the piano's sound. The audience sits much further away... in the far field.. and thus likely hears a typically overtoned spectrum, no matter how you string the harp. The audience is hearing sound enriched by the modes of the sound board and splayed off the lid. This is my initial thought; I'd be interested to see some data, to see if I am right.
Moreover, the cross-string design came into being for several good reasons:
(1) A cross-string piano is much more compact;
(2) Crossed bass strings pass over the middle of the sound board, giving better resonance;
Furthermore, I speculate...
(4) Technicians have been working on cross-string grands for ~150 years and I suspect this new (old?!) design will present new maintenance challenges;
(5) The forces on the harp are probably better balanced with cross stringing;
(6) I'd expect better overtone resonance with a cross string design, i.e. more cooperation between the strings.
So will the Big Barenboim succeed? I doubt it. But it's still interesting!