I think it might be better to not show Luke flying out of the DSII at the last second. Maybe show the shuttle small and in the background as Lando flies out (or just as the DS explodes if Lando doesn't make it) but it would add to tension if we last see him grieving over his father as the station is under attack and we're not entirely sure that Luke makes it out ok until Leia's "I can feel it" line. Up until then the audience could be left to wonder, since because Leia's alright that means Luke may yet be expendable.

And responding to the aforementioned ghost idea, I'd still prefer it to stay as the 3 Amigos at the end (Yoda, Anakin, and Obi-Wan.) They're the ones who knew Luke, and it would seem that at that point Luke is the only one who can see them, either by their choice or his ability.