The more specialized cruiser have 2 advantages over the versatile Odyssey.
They are cheaper and handle better and of course come with different abilities.
I believe the Ambassador will be the science counterpart to the tactical Excelsior (allthough, in-universe I would have liked it better the other way around).
That means a Commander Engineer, a LC Science, a Lt Engineer, a Lt Tactical and most likely a universal Ensign.
Handling will hopefully be closer to the Excelsior than to the Galaxy, at least on Sovereign level.
Special ability could be anything. Maybe somehow a reverse version of the Wells' ability. Instead of a time reverse a time jump forward (whatever good that will do).