I love it. It's very poetic and harmonious and believable. I believe in this Draco who wants absolution. There are enough elements in Cannon (for me, as early as book 4) to think he might regret his forced association with Voldemort.
Well, other, very different incarnations of him make sense as well, but I like that one.
The idea of the pure-hearted unicorn as a proof is wonderful!