(humor, off-topic)
This sounds like a Star Fleet Battles discussion.
For example, we have the Klingon D7 Heavy Cruiser, but this is a more advanced version of the Klingon D6, which were - are still are - often used as Prison Ships. Some D7s and older D6s are retrofitted as D7Ds and D6Ds, which means they are Drone Heavy Cruisers, able to fire a large number of drones (thermonuclear missles capable of transwarp speed.)
Some D7s enjoyed an upgrade to their phaser banks, giving them PH-1s in the forward Boom, instead of the PH-2s with the inferior fire control (a problem the Federation solved but which plagued many other races for decades.)
A couple of D7s were modified, I believe, to become Maulers, where most of the systems were ripped out and replaced with batteries, and a giant transwarp gun put in place to blast the energy out. This could blow away enemy ships in one mighty hit, but it could wreck the Mauler in so doing. The hull just wasn't built for such purposes.
When the General War started, the Klingons realized the D7 was cost ineffective, so they ceased production of this Heavy Cruiser (they had enough of them, in active fleets and in mothball, in any case) and began the production of War Cruisers.
The Klingon War Cruiser used a smaller and cheaper hull, and had far fewer systems (it was ineffective as a research and exploratory ship, unlike the D7), but it had the same firepower and shield capacity, and the same power capacity, as the D7. The War Cruiser came in 2 variants, the Heavy and Light War Cruisers. These heavily modified D7s also came with new and improved drone racks, and vastly improved drones.
Some D7s were modified to be Carriers, and became known as D7Cs. This didn't entirely work out, since they could not carry enough fighters and they had to strip the armaments out of the ship to make room for the hangar bays. But fighters were far cheaper to build, so if fighters took out expensive enemy ships and you lost the fighters in so doing, you won (a point the Klingons had learned well from their battles with the Hydrans, the Ultimate Fighter Race.)
When small warp engines came into use, they invented this hideous monstrosity known as a Fast Patrol Ship. Built on a tiny hull smaller than that of a frigate, and quite cheap to produce, they had the firepower of a Heavy Cruiser (D7 and others.) They didn't last long in combat, but they tended to eat enemy ships for dinner, and losing them cost the victorious power nothing.
Some D7s were equipped with mech links (specialized tractor beams) in order to carry these nasty little warships. Again, though, it didn't quite work out. A larger hull was needed than the D7 possessed, and the C8 and C9 dreadnaught hulls, and the mighty B10 battleship hulls, provided the needed size. Specialized PF Tenders were also produced, to carry 6 of these little monsters into battle (the tender had no weapons, but the 6 little ships were like 6 Heavy Cruisers coming at you.)
The Klingons were never able to make a Space Control Ship out of the D7. It simply didn't have a big enough hull. What was a SCS? It was a Carrier and a PF Tender, and it had the weapons of a Dreadnaught. All the races built several of these ships (the Klingons gleefully converted one their B10 superships, into an SCS.)
But the D7 never made the cut.
By the end of the General War, most D7s had been destroyed or so modified as to be unrecognizable, or simply retired and the parts used for other purposes. That was the end of the D7 design, or should have been.
Except that those scientists working on the problem, came up with a whole new set of technologies, applied them, and created the DX, or D7 X-Ship, a highly evolved ship capable of running circles around other ships. The Klingons were amongst the first to create an X-ship in this fashion.
X-drones and X-fighters followed (but not X-PFs ... the superior shields and firepower of X-ships made them obsolete), so the DX became the workhorse of the new fleet.
Due to the invasion of the ISC, and the temporary peace it caused, the Klingons had time to produce quite a large number of DXs, and just in time to save them from the Andromedans, arriving with their alien ships from that nearby galaxy. Unlike other races, the Klingons withstood the assault and held most of their territory. The DX played a crucial role in making this happen.
There was even a D7 scout, although only one or two since D7s were needed for other purposes. Equipped with Special Sensors, scouts explored in peacetime, and played Electronic Warfare for fellow ships, fighters, and PFs during wartime. A most interesting thing, for they came with 2 points of ECM built in, and they could produce 12 points more (of ECM or ECCM) and keep it for themselves, or loan it to other ships/fighters/PFs.
Nimble ships and fighters already came with ECM of their own, ECCM was a power consuming affair, and a lot of objects could lend their own ECM. A lot of ships fired at point blank range, only to see their Phasers did little and their Heavy Weapons miss. Not a pretty sight.
Where is the Retro in all this?
Most of the battles fought were *not* fought with the newest, latest equipment, but with old, antiquated equipment (you could count on the military spending the money elsewhere, not on you and your ship. Or, if you somehow attained importance, Klingonese politics came into the picture and you got demoted to the D6 Prison Ship for some incompetency or minor error you did not commit.)
If the phasers worked, if the disruptors fired, if the transporters and tractor beams worked, if the ship made it out of the Starbase without half of the rotted internal circuitry not burning up (much less when you blasted off into translight) you could count yourself lucky. They didn't call these Mothballed Ships for no reason. If there was a single drone in the drone rack, or more than one shuttle that actually worked, or a single transporter bomb, you were pretty lucky.
Your one break? The Other Side had the same problem.
Now, that's Retro. As Retro as it gets.
You could have had the Phaser-I upgrade. Speed 30 (Warp 3) drones. Scatterpacks. 10 Transporter Bombs. Special Shuttles. All sorts of ship upgrades. Instead, you had a cloud of dust everytime you sat in the Captain's Chair, and the viewscreen wouldn't work half the time you asked for it's use (not that you wanted to see or talk with the Hydrans anyways, but still ...)