They actually have been performing on Shabbos all through previews, taz. I heard Eric Anderson on WNYC's Soundcheck talk about how they hadn't done that in any previous run of the show but chose to now, and that apparently those audiences have been great. Then again, I saw it on a weeknight and my mileage may vary from Mr. Anderson's.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.