In this question and especially it's accepted answer, it is established that the name 'Vader' was plucked from the Force in the moment of his rechristening.
Now, Sidious had been planning to seduce Anakin Skywalker to the dark side for, well, a lot of time. Is there a reason given in the novels, novelisations or anywhere else which explains why - despite all his planning, scheming, manipulation and preparation - he never planned for what 'Darth' his new, best-ever, more powerful than himself apprentice would become?
Surely you would think of it, plan for it, try different titles out - even think of it as 'The Vader Project' or similar? Is it perhaps part of the Sith tradition?
Why did Darth Sidious leave the name for Darth Vader out of his meticulous preparations?