I'm going to say ginny as a use her and toss her aside like trash slave... I hate her... hmmm hermione I like, so I could see her as bonded, if not definitely slave... beyond that, I like fleur and gabrielle as bonded, either or both... padma patil, NOT parvati... su li is a little used character that I always like seeing in this kind of role... susan I like as bonded... hmmmm vector or sinestra or both as bonded or slaves, operatives in the castle... there's also the fact that for the 'slave' class, they don't have to be SEX slaves, so he could do something like make snape a slave, KNOWING that will make him loyal, etc...
I'm hoping this isn't the power he knows not, since I like super!Harry... and I'm also hoping that being 'bonded' means Harry can use their abilities, not just magic, meaning Harry is now a metamorph, etc.