Something is going to happen to the TOS Enterprise near the end of Pike's Captaincy that the SNW Connie gets soo beat up in a battle, that once it gets repaired, it'll eventually shrink from the SNW's length of 442 meters, down to 289 meters of the TOS Connie and get handed over to James T. Kirk for his command, while Pike moves on to Admiralty.
If you can borrow the parts of the original USS Titan and shove it into a Neo Constitution Class and call it the Titan-A, there's no reason that after a severe battle where the SNW Enterprise will eventually survive, but limp home very bruised and battered, that a fixed up Connie will end up shorter / smaller due to updates in it's design and just be called the "Constitution Class".
At that point in StarFleet history, they won't have thought of appending letters behind the ship because upper brass doesn't think it's worth doing so.
That would easily fix "Canon" and solve the SNW Connie & TOS Connie length / size issues.