I'm a bit iffy about it as well, however "To, by vote of the Consensus, abolish the Consensus" really strikes a good cord with me as even if I am very cautious of the "to a single sovereign" at least it would be by vote of the Consensus. It'd be non-violent and in-hand with the law. Personally, I doubt the Consensus would even think of voting for anyone other than an individual of "unimpeachable character". Much less even consider voting for the idea at all.

Even if at the start of this vote the candidate is pure, over his long, unimpeachable rule he may become corrupt and this has no way to deal with that (I bet they try to vote a new monarchy person in anyway)

Aye, luckily it'll be long after the Darkness has been made null. With that in-mind it'll be up to the people to deal with it as history has it's funny way of going about it. Remember, these lads have access to any History that's common knowledge at the time. Like say ancient lessons learned from past Monarchial societies. Not guaranteed of course but as long as we live under the Traveler's Light it should be quite fine.