I never though of Snape as continuing as a spy for his career or as becoming an unspeakable. Yet now it seems so natural, so right a fit!
Snape was such a good spy and with his brilliant Occlumency and Legilimency skills, he'd be a brilliant Unspeakable.
Meanwhile I agree with Hermione that I can't imagine why the powers that be would let those two be in charge of the unspeakables. They're both, but especially Ron, so prejudiced and judgemental!
Brilliant story. Loved it. Would enjoy reading more adventures from Severus Snape, Unspeakable, at your service. *giggle* aww, he was so excited about a job, FINALLY! :)