I wonder if Jack will contemplate killing himself perminantly whilst he's got the chance? It's something I would love to see and something RTD has hopefully thought about.

The only problem with Jack contemplating permanent death is that I think his sense of duty won't let him do anything until the whole 'miracle day' situation is resolved, and by then it'll be too late for him.
Of course given the light hearted optimism that RTD is soooo well known for in all his works, I would be quite unsurprized if the final episode includes a scene of Jack trying to top himself, only the 'miracle day' is over and he's immortal again.