Mario de Monti wrote:
The intent of this thread was (correct me if I´m wrong anyone) to find an in-universe explanation, as to why Starfleet would go to such trouble to completely rework the Enterprise instead of just building a new one.
Okay, an in universe explanation. Here's a possible one, I remembered reading and got the novel. It's from "The Great Starship Race" by Diane Carey. At the very end of the novel the Enterprise had taken very heavy damage and was due for repairs. This quote is Kirk talking to Spock about the repairs:
"And I don't want anything replaced that isn't in pieces. The Enterprise just showed us how tough she is. Her spine, frame assemble and exostructure turned out to be a lot stronger than we thought. Even stronger than her designers thought. I don't want any of that strength repaired out of her."
Maybe Kirk, and I assume Scotty would agree, wanted to keep as much of the original Enterprise as possible and simply upgrade instead of replace the entire ship with a new one.
Except, Decker tells Kirk that the refit is an almost totally new ship. So different in fact that Kirk has trouble finding he way around it, doesn't know how the new engines and weapons work, and there's hardly anyone rated on the design according to Decker.