To take the first part first: should the Pope be arrested? This is extremely difficult to answer. Did the Pope engage in reprehensible activity? Apparently yes. I would classify mandating the systematic concealment from legal authority of such crimes as child-rape to be reprehensible, and that appears to be only one of a group of reprehensible actions of Ratzinger and the RCC (Roman Catholic Church).

Would that activity be criminal in most other individuals? Undoubtedly yes. Is that activity a crime for which the Pope, as probable perpetrator, can be arrested? That is the million dollar question, and I would say it's not been clearly answered yet. It is complicated by the history of the Vatican as a state, and the lack of precedence for prosecuting heads of state for crimes other than war crimes or genocide. It's unclear whether or not there might be a loophole around diplomatic immunity given the specific history of the Vatican.

I would personally say that international law should be established to permit prosecution of such practices if it is not already in place, but it's unlikely to happen. The RCC holds a great deal of political sway. Unlike many nations, it is tiny but has a huge presence and influence (and wealth) within other countries, which it can then use to insulate itself and its clergy.

There is also the glass-house problem, where other countries have engaged in activities less than genocide but that perhaps ethics demand should be prosecuted (for example American torture activities, and the indefinite detainment of individuals, without charge or trial, known to be predominantly innocent). I suspect a lot of governments operate in enough grey areas as to make supporting this issue detrimental to their own health, and politicians are nothing if not self-preserving.

Will Hitchens and Dawkins help bring about the arrest of the Pope? No. I really would prefer it otherwise, but if it were even remotely likely to happen the British government and the Vatican would take steps to ensure it did not, probably with the support of much of the international community (at the political state level, not necessarily individuals).

What if the Pope were arrested? Can the Pope be removed? The Pope can choose to resign, if he so wishes. There is no mechanism, so far as I can tell, for the RCC to remove the Pope should the Pope not wish to resign, even if he were arrested and imprisoned. There is no historical precedent for arrest of the Pope on criminal charges of the sort being considered, although Popes have been taken prisoner in a military context.

What impacts would his removal have? Herein lies the probable reasons for why he won't resign unless truly given no possible alternative. Popes have done all sorts of immoral, unethical, and bat-shit crazy things, yet the last Pope to resign did so 600 years ago.

There is no modern precedent for the moral and criminal culpability of a Pope for their action and inaction prior to or during their Papacy (pay-pah-see - I heard it mispronounced on a podcast, so that's just in case anyone's unsure how to say it), and Ratzinger is highly unlikely to encourage such a perception of culpability, not only for his own welfare but for those of the RCC and its clergy.

How many other priests and higher up would be exposed if any kind of in-depth investigation could be carried out (it won't, but speculate on the numbers for the sake of argument)? Vatican City has a population of only 826, according to Wikipedia. What percentage of the serving clergy might be involved in cover-ups that could come to light in the future, even without a trawl through internal Church records?

To take this line of thought even further, how many of the Holy See might be pedophiles that were successfully shuffled such that their crimes never came to light and they were able to progress in the Church? I speculate, of course, but it is not hard to imagine that the Church might hold clergy close to its bosom whose dark secrets they have worked even harder to conceal than those that have become public knowledge. Look at secular authorities and the ethical failings that are so commonly demonstrated. Surely the Holy See is likely to suffer the same human failings, and yet we know from demonstration that if they did, the Church would hardly expose them, but manage them in secrecy, pretend they don't exist, and restructure until the trail of any crime is cold and lost, even at the appalling cost of exposing further potential victims to a sexual predator.

The only thing worse for the wellbeing of the RCC than being exposed for the hive of moral hypocrisy that it is, would be to say or do anything that would imply they should be held accountable now and in the future for that hypocrisy, and for the evil of their actions.

I support any action that is taken to bring the perpetrators and abettors of these crimes to justice, be they priests raping their young charges or upper eschelons of the Church knowingly shielding them from criminal repercussion, but I doubt that anything materially will come of it. I hope I'm wrong.