You'r probably right. At first, I very much downplayed their mention, but their introduction seemed to affect the mission roles that the Excelsior class was later sent on - stealing away some of the more prime exploratory and diplomatic missions. So I felt it was worth a mention.
Don't get me wrong, I very much agree with documenting how the Ambassador affected the Excelsior class. I'm just not sure I'd go much more into the Ambassador history past that. Certainly not how the Galaxy
affected the Ambassador. (Gotta save something for the next book!) But did the Galaxy affect the Excelsior class? - they are contemporaries. Heck, the Exies share space with the Sovereigns! But I notice you're not done yet either.