I like this! This however made me think -- going back to the Transwarp subject; as you know it really bothers me that a full scale mock up was made before thoroughly testing the concept smaller scale. Earlier we talked about a compromise, where it was only a partial failure.
Another thought occurred to me. What if the Excelsior in ST III functioned just as well as it was expected to -- that the limits and extent that they could achieve Transwarp were known prior to starship construction. In other words, prior to ST III, they knew the Transwarp experiment would not result in the "infinite speed" or breaking the "warp 10 barrier", but kept the project name for PR.
In reality, Transwarp was dropped for political reasons -- Transwarp as a concept was simply a plot device to allow our heros to be the underdog in TSFS. After TSFS, the producers had little interest in the concept, and the production team of TNG seemed to consciously distance themselves from many of the concepts from the films.
When trying to divine an in-universe rationalization, I find myself wanting to mirror the real world reason. In other words, since transwarp was abandoned for political reasons production wise, why not assume it was abandoned for political reasons in universe wise too? I don't know if this is a good approach -- this may in fact be the wrong thing to do, allowing the production reality to shape the universe that we want to be "above" such considerations.
Yet in my mind, it makes a certain sense. Kirks actions in TSFS contributed to a very tense and sensitive political situation (the Genesis project and planet) blowing up in Starfleet's face. Though Kirk's actions in TVH led to his actions being all but pardoned, we have little indication that the overall political situation was resolved or even improved. Rather, it was simply deferred due to a more imminent crisis.
I could see Starfleet, in the immediate aftermath of events of TSFS, putting a hold on Excelsior trials as the leaders scrambled to contain and address the political fallout from all sides. Indeed, a freeze on R&D may have been imposed on any cutting edge technology that could be construed as providing a tactical or combative advantage. Agreements such as Federations abstention from cloaking technology might have had their genesis (no pun intended) here.
When all the dust had settled, and the federation had brought some stability to the situation, an edict may have come down to discontinue use of the term "transwarp." Starfleet would then quietly close out the project, officially labeling it a "failure" (which technically it was determined to be long before the Excelsior was built), and discretely make improvements under the guise of enhancements to "conventional" warp drive. And Admiral Harry Morrow, the man who spearheaded the project, quietly stepped down from his role as Starfleet Commander.
The hit to morale would be substantial. During this decade, and in spite of their efforts to the contrary, Starfleet found itself becoming perceived as more and more militaristic. Border disputes, raids on colonies, bottlenecks on the supply of resources pushed Starfleet deployments more into this role.
Excelsior project was heralded as a beacon of light, with hopes that it would bring exploration and discovery back to the forefront, returning Starfleet to a new scientific era. Alas, what began as a shining talisman to the future soon became an albatross of the past. Starfleet would not see a return to this era for another 80 years. It is not without irony that Excelsior's commissioning plate came to have the quote "No matter where you go, there you are"
To be clear, exploration and discover were never abandoned. Several new cultures were discovered and relationships forged. This issue was simply that Starfleets overlapping roles of exploration and protection, which always necessitating careful communication and education for both member and non member interactions, continued to become more blurred and nebulous during this era.