PP, in an anarcho-libertarian society, the leaders would have almost no power, anyway, so this is irrelevant. Granted, in an authoritarian society with enlightened despots, we would need further safeguards, like the ones I already mentioned. For example, if a particular royal family had, say, 150 people eligible for the throne, at least one out of those, the best one, could be elected to power by those eligible to vote(only the best being allowed to vote, of course). Plus, if we had a system whereby royals who turned out, unfortunately, to be incompetent, were removed, then Nicholas II etc. would never happen. Bear in mind that it took a very long time for the Russian Revolution to happen, so measures taken well beforehand would have sorted things out.
And, no, I am no particular fan of the Tsars, it's just that there are several examples of enlightened despots among them. Nor am I a fan of HRE, I just cited them as the emperor of the HRE got himself elected to power, not just gaining the throne by right of birth.
As regards testing politicians, that's not a problem. If one had private investigators checking all aspects of a politician's life, skulduggery would be difficult to keep hidden. Plus, in an anarcho-libertarian society, the individual would have most of the control, so that bureaucracy would be unnecessary. This is going to be much easier as technology advances. Take for example the fact that bacteria are being produced which feed on sewage. Imagine a future in which one can buy bacteria dirt-cheap which can break down any rubbish, even metal. Then one wouldn't need council rubbish-collectors any more, and so on and on.....