I think that just a few designations are better. In my opinion the longer names seen in the fandom like "advanced heavy tactical command frigate" might exist in the sense that they explain why two designs/classes of similar size or configuration might coexist, but I cannot see them being used in regular daily parlance.
The problem with Exploration Designations is that most of StarFleet are different variations of "Multi-Function All Purpose Explorers"
Size determines how many different type of scientific missions can get done and at what rate, thats it.
It also determines the capacity of your Engineering, Hospital, Diplomacy, and Surveillance capabilities.
I'm rather fond of the idea that the typical starship is but a shell. What gets embarked for a specific mission dictates the ship type: under the command of Pike in "The Cage", the starship was a humble Sloop, with just 200 crew and logistics modules for supply runs. But under Kirk in TOS, the starship was a Cruiser, with 400 crew to operate a broad set of research and combat modules...
This would support the idea that in general use, they are not many different classifications in use. Pike version of the ship might be just a cruiser, or even be a light cruiser, and Kirk's version a heavy cruiser, but I would expect both to be called "Constitution (or Star Ship) class" by anyone but a drydock master. In the heat of battle, the general idea that the ship is a well-balanced cruiser is likely more relevant than knowing whether is something like a "defensive strike armored light cruiser" as opposed to some other type of cruiser.
I follow SFB/Starfleet Command also, mostly because I was the most impressed by how it filled out starfleet. Those military categorizations also effectively described the capabilities of the ship in scientific and patrol duties- ie Cruisers are the most balanced of the fleet. Dreadnoughts and Battlecruisers have more weaponry, but also more amenities due to their bulk and size. Klingons refer to the Enterprise-D as a Battleship, the refit as a Battlecruiser, et all.
I also think ships get re-designated as they get older. Excelsior started life as a Dreadnought on the boards, got downgraded to a battlecruiser when she had sister ships, and by the 24th century she's just a heavy cruiser.
Same thing with Mirandas. They begin as New Heavy Cruiser replacements for the aging Constitution/Enterprise class, get overproduced and end up in the 24th century as mere frigates. As (cold) wartime classes oddly they end up being more viable and long-lived than the 24th century replacements which were either too optimistic in their capabilities or too watered down for peacetime roles to be as long-lived.
Like I said, those other classifications might exist to explain, for example, the difference in role between a Soyuz and a Miranda, but calling them a cruiser or frigate keeps it simple and effective in battle.
I also agree that the Mirandas and other classes were likely downgraded as they stayed in service while other bigger classes were brought into service.
Although optimized for combat to a certain extent, Starfleet's destroyers are another "do everything" design that is deployed in substantial numbers, probably 100 to 200 or more.
100-200 destroyers at any given time would make sense with they way I expect NCC numbers to work, as some ships have numbers like 12999, meaning that could is a destroyer type ship and this is the 999th vessel built. It also means that 12 could be more a designation and less an indication of actual class.
Back when I was writing fanfics, I kept my ship classification system fairly simple:
(from smallest to largest)
- runabout
- escort
- science vessel
- cruiser/frigate
- tanker
- explorer
Ships could be rated as "light," "medium," or "heavy" in their specific classifications, but I always kept them as subcategories. Hospital ships fell into my cruiser/frigate category too. I kind of imagined a runabout as an "ultra-light" starship, with greater operational range and other abilities than a shuttlecraft.
A short set of terms like this makes sense for daily use. Here is the version I think about when analyzing the series, modifying the TNG tech manual system.
Explorer (peacetime name for Battleship)-big, expensive, only Galaxy and newer
Cruiser-general use ship, on the big side, covers most hero ships up to Ambassador
Cargo Carrier (peacetime name for Fighter Carrier)- big, but unlike the real Navy, smaller than a cruiser, Akira would be an example.
Tanker-smaller, still capable of general duties, or carrying supplies, like the Ptolemy.
Surveyor/Escort (peacetime name for Destroyer)-small, operates on the edge territory, mapping and some border policing, but can also carry cargo (Antares from TOS)
Scout-small, fast, plentiful, inexpensive, (Grissom would be a newer example)
So that keeps it down to 6 quick designations. But, an Intrepid and a Steamrunner might both be Destroyers with different longer classifications, but I don't like to use them often
