I actually had a question while thinking about this fic while I was at work. What's Dumbledore's Nature?
Then I had an epiphany as to why he did what he did. Dumbledore's not a dominant, but a sub. His dominant was Grindlewald and Dumbles bound his own nature in order to be able to defeat his dom.
So he figured that Harry would be alright if similarly bound, as Dumbledore is moderately alright (except he's not and just needs someone to slap down his more manipulative tendencies).
Author's response
Interesting premise - my idea for Dumbles' Nature was similar, that he was a Sub who repressed his Nature because he felt the concept of NAtures to be demeaning/bad etc. If I use your idea with Grindlewald, Ill credit you