The terrible thing is that
a) I cannot help but imagine that this would be better than the real ending, whatever it was and
b) I can just see them actually doing this
I imagine it being done in montage, with the Doctor helping out using the Tardis, then as a witty finale the Doctor (probably 9 in a guest reappearance) asking Jack if he fancies a quickie, and then Jack saying 'sorry, I've got a headache'