The coin gif is already in use, which means it's royalty-free (I'm assuming), and it's not hard to re-color the existing image that you're already using. The look is uniform, and it matches well with the existing feel of the forums.
I modified the milestones a bit, and maybe you could add a half-coin accent (for the fifth coin) for anyone that submits over 10,000 good reports (to match the existing rank icons).
Sometimes the most subtle changes/additions are the most effective ones. Thoughts?
Put aside those milestones change, I agree with your idea. Any other designs on this thread are so beautiful that overshadow the ranking badge - which is unnecessary for a secondary badge. Anyway, the color is a bit over colorful, grey would be better