So back to the Enterprise-A, the idea of a technology demonstrator makes a whole lot of sense, especially given the relatively futuristic appearance of her systems at the end of ST-3 and 4. While we know the real-world reason, in-universe for her to be furnished as if she was a galaxy class makes little sense. But if she was a showboat to what would be coming in future starship deigns, then her being able to be quickly renamed and retired after a relatively short service life makes sense. We can further infer that while the upgrades might have been good for drydock tours or short flights in the solar system, long term the designs had serious teething issues, hence her relatively downgraded look in ST 5. Same thing happened to Excelsior, when we first saw her bridge in ST-3 compared to 5.
