Agreed (I get the impression this was how it was supposed to work in canon as well, with the chief difference being that Voldemort was much weaker and avoided taking direct control, so Quirrell was still capable of attempting wandless magic by the end of the year). I'm actually a little curious as to whether or not the unicorn blood detail has any relevance to HPMoR, but it hasn't been mentioned yet that I remember, so probably not.