I think they should play the rehearsal footage on big screens at the O2, record the audience applause and reactions, and combine the two for a dvd. Maybe on a dvd have the option to turn the crowd track off for purists. simple and tasteful.
Or perhaps still take this is it to the O2, but only have the band and the dancers with an empty space on the stage, and bill it as a mass singalong for the crowd to sing along.
Either way it's too soon to speculate. Lets rather think about the man's life and celebrate him, rather than think of our DVD collections and how to get a piece of the pie...at least until he's laid to rest.
Jeremy.