Say a person was granted a responsibility role after working hard. The person accepts the role with gratitude and pride, almost as if it was natural to achieve the role. However the decision of assigning the role is not taken by the person, but their superiors, and the person had the chance of refusing the role if they wanted.
In this situation, I can't find a way to stress the fact that the person took the promotion with "proactivity". Verbs such as "being promoted" or "being granted a role" are in passive form and sound like the person had no choice but to accept, or as if the role was just a promotion instead of a challenge. On the other hand, saying that the person "accepted the role" or "took on the role" leaves out the shade of "promotion" that the other forms retain.
Sample phrase, with an "incorrect" verb taken from above:
"Mere days after his trial, Jonathan was promoted to team leader."
How would you express the phrase in the most expressive way?