Possible reason for giving Snape the job

[Missy]

No: HPFGUIDX 135431

Not the job at Hogwarts, but the job as DADA Professor.  

I've been thinking about this a lot, actually.  And I think one of the 
reasons that he got the job is because of McGonagal.  She made a vow 
that she would see to it that Harry was made an auror.  And I think 
that maybe she convinced DD to give him the job, so that someone else 
could do Potions, and based on Harry's OWL grade, he would be able to 
continue his coursework.  And that would enable him to eventually 
become an auror.

Missy (Who is still a E!SE Snape person)