I was thinking for quite a while about sending this question to Maria Zuber's e-mail address (she was the principal investigator of the GRAIL mission to map the Moon's gravity field), but then I thought that it may not be appropriate. Also, asking her whether she or her collegues have considered this idea. She has been involved on the Clementine mission to the Moon, MESSENGER mission to Mercury, and MAGIC proposal to Callisto, all of which have included gravity mapping and laser altimeter investigations.
My question is simply whether we have the technical ability to perform a similar mission on a much more distant body.
Or, in other words, whether this mission has only succeeded thanks to the fact that it happened on the Moon, where; precise tracking, higher data volumes return, signal delay etc... are greatly facilitated by the shorter distance.
The key to its high sensibility is how well they managed to keep the two spacecraft flying in formation, and how precisely they managed to track the deviations caused by gravity anomalies. By the end of the mission they even managed to orbit at commercial airliner height.