I think What Abrams could have done is include the full uncropped 1.44:1 sequence as a bonus feature in the Extras section of the Blu Ray (in addition to the shifting ratio on the 3D BD). In that way we could see both the standard 2.39:1 version of the film as well as the original IMAX framed sequence as it was shot. 2.39:1 to 1.78:1 is not bad but we are still missing a lot of image vertically from the original IMAX framing.

From the IMAX stills I have seen, the 1.44:1 framing is beautiful and has that sense of vertigo and immersion, but a 1.78:1 crop will lose all that feeling.