Particulary, after completion of all objectives in this last phase.
Right now, if you abort the mission at this point, it still counts as done and you can't run it again -- the only difference being the lack of payment at the end.
What if you want to check out some alternate scenarios ways in this phase? Like it very often happens in contact missions? Such a little change would be certainly very helpful in such occasions.
I don't see any counterpoints to this (I mean, what other purpose would it have to abort a mission just after completion? And it's hard to do it accidentially in any case).