That is great. Much as I love the face of boe, Jack ending up as him is just wrong. This is a wonderful and plausible route to go that doesn't just save Jack from a fate worse than death (all that time without sex? This is Jack we're talking about!), it redeems RTD from the circle of hell reserved for bad writing.
And anyway - Didn't Gwen say before (in countryside) that you can never tell when Jack is joking?
Love love love. :D