[err4nt]

My take on the situation is that if they are hiring the first (pre-approved) person to say 'Yes!' for a position, then they care more about the position than the person. My gut says that you wouldn't have sufficient job security, because to them, even in the hiring process you're expendable and intercheangeable. You're lucky if they used your name instead of 'Dear Applicant' so they could just blast out the same message to all candidates.

Work for people who value your person, and say: "I'm willing to pay x dollars to have YOU on the team!"

If it was me and this situation went down, it would be hard, but I would reply with this: "I would love to work with you, but at this point it doesn't seem clear that you want to work with me. Let me know when you are certain that I am the person you want on the team, and we can talk about my availability at that time."