Re: So many Mirandas/So few Constitution-refits?
There was also the Bozeman that lacked a rollbar prior to the Soyuz-class retirement not too long after "The Undiscovered Country".
And in early DS9 we saw Sisko's Saratoga that participated in the Battle of Wolf-359 which also lacked the rollbar. It wasn't until the Dominion War kicked off in earnest that we saw a resurgence of Mirandas with the rollbars, IIRC.
The Bozeman was a separate subclass and not a standard Miranda, and one could argue that the same is true of the Saratoga (I know one offscreen source that treats it this way, with the Saratoga having been modified to be lead of a new class). Since the modified Saratoga didn't appear until DS9, I was mainly referring to those ships we saw in TNG.
"If you think you're brave enough to walk the path of honor, then follow me into the dragon's den."