Or whether the Sovereign
was ever intended to fight in separated mode. After all, while a separation line of sorts was designed in, there apparently was no thought given to providing the "Battle Section" with things like impulse drive... Just as with Kirk's old ship which supposedly was incapable of doing anything much once separated.
Kirk's ship had a "Battle Bridge" or three despite not having any operational separation ability. We never quite learned where these were located, though, and we got no real reason to think they would be better protected than the Main Bridge.
Not until a bit of thought was put to the layout of the refitted ship in ST:TMP, that is; both Andy Probert and Shane Johnson tried to put Auxiliary Control in the very middle of the saucer, even though the sets didn't exactly make that easy. We never saw such a facility in the actual movies, so we didn't get any wiser in the canon sense...