Without creating a new universe, then...
I have no problem with advancing technology. But not a different setting. I want the Great Houses and Clans to have fleet units, and their own developing naval tech. I want to see the naval side of the Inner Sphere and periphery get developed more. Not neglected while considerable resources are devoted to a completely separate setting.
At the level of what you are suggesting, you might as well just create an entirely new science fiction universe setting with zero ties to Battletech. For all practical purposes, it is that.
Okay, so how do we DO this?
There are some base assumptions we have to work with:
1. The mechanics of how KF drives work.
2. The mechanics of system jump-points.
3. WHY do past practices in the fiction matter, and how can we work with, or around them?
4. the agony of managing the logistics so that we don't end up with hurling massive, identical fleets of Leviathan variants at each other.
5. Same for managing classifications.
Item 5 feels like a decent place to start, because it starts with "Why did they build it?" Not the fluffy reasons, but the game-mechanical ones.
With Battlemechs, Tanks, most forms of vehicle, and even ASF's, we have defined roles managed by size and scale. While someone DID build a 'scout' Assault 'mech (the Charger) it doesn't work well as a scout, because
it's an assault 'mech.
Likewise, you have to be Kai Allard Liao or Phelan Kell to stand a chance, solo, in a light 'mech against most assaults.
so what is the order of battle, and
why?
first questions we have to answer if we're going to see real progress on Naval in the game.
basically we've got movement rules, we've got tech, we've even got designs. What we don't have, is a clear and useful picture of how to put that together in a way that doesn't violate
something-whether rules, science, or common sense.
I started a thread and it went off the rails over this in the rules forum. Someone else did the same, and someone else besides them...
but let's try this approach:
What is a Navy FOR??What is the purpose of a Navy? What should it do, what does it do, what can't it do?
we've got LOTS of systems, but how do they work into a structure you can build a campaign around?
With that first question, you're already hitting more notes than three generations of game developers and authors.
Here's some possible answers:
1. Your Navy is your secure line of communication between holdings.
2. Your Navy is your guarantor of safe Trade within your interstellar nation.
3. Your Navy is your main means of moving Ground Forces to and from targets and garrisons.
4. Your Navy is what protects your supply lines.
5. Your Navy is what gets your ground troops out of a tactical disaster.
6. Your Navy is the first line of contact with neighboring realms, both in peace, and in war.
Those are six general classes of function that a Navy (that is, a service whose primary focus is on Ships and movement) should be able to carry out with a fair degree of competence.
You'll notice I didn't emphasize the combat role there. this is because per canon, all of the Great Houses relied on civilian-model jumpships extensively for their Navies.
This is the working navy. the 'fighting navy' has to fill all six functions, but also has to fill the following:
1. Your Navy is the eyes of your Nation, it handles reconaissance on a STRATEGIC scale, both in peace and wartime.
2. Your Navy is your best means of cutting the other guy's supplies off.
3. Your Navy is your best bet for knocking out your enemy's lines of secure communication. (Comstar is, by definition, NOT SECURE, handing your classified traffic to a foreign power on the promise that they won't look at it is an act of utter irresponsible stupidity, and likely grounds for a coup.)
4. Your Navy is your best economic weapon against hostile states, by targeting a hostile's supply lines and commerce. (Commerce Raiding).
5. Your Navy is your best means of relieving sieges or preventing landings. Navies that attempt static defense have a name: Easy Targets. The Navy must be mobile, and able to present a threat (even a minor one) to enemy forces on the attack.
6. Your Navy may provide ground support fire to landed ground units. (This is a bad idea, but it's a popular one.)
Okay, so that's six 'general-general' roles, and six 'combatant specific' roles.
Why am I oversimplifying? Because this is a GAME, and not an accounting exercise.
we also have to deal with the elephant in the room of Fasanomics, because after nearly 40 years, nobody's been able to satisfactorily set up an economy in the setting that doesn't violate common sense like a really violated thing, staked out to be violated even, with no recourse to the violators.
Setting Fact: we don't have Stargates or teleporters, we don't have Inertial Dampeners and we don't have structural force-fields. We also don't have Replicators (either Star trek style, or Stargate SG-1 style), and we don't get to have reactionless drives, artificial gravity (aside from spin or thrust based).
That sets up our basic conceptual elements: Ships have to carry everything they need to keep their crew (and passengers or prisoners) alive, and they have to refill it because we also don't have perfect recycling for our life-support.
There are defined limits to KF drive size and performance-we don't have jump-capable fighters, they have to be carried.
Thus, we can make a few assumptions:
1. Bigger ships will tend to have longer life-support duration than smaller ships. (along with more fuel, more food, more water, more medicine).
2. Most navigation will be between stable points, because of the limits on Jump drives.
3. Because excessive high gravity is bad for human beings, and especially for ground forces, approaches to planets for assaults will tend to be at one gee unless the attacker wants to lose the surface battle.
Flank security is kinda important, because a navy on the defense doesn't have to keep ground troops fresh for their landings, and can essentially guarantee their own personnel are strapped in, strapped down, and fitted with Gee-suits or the equivalent, with hundreds to thousands of hours of training in how to endure brutal shifts in relative gravity.
which ground troops really don't have that luxury.
So, you need transportation, and you need protection for that transportation,a nd it can't always be the same thing, because if your escorts can't keep up with an opfor's attackers, they're useless.
4. Because most combat is going to occur as a result of movement, this stuff matters. If an invader can't land his troops, his invasion is done. If a defender can't protect their trade routes, they're of no value, and if a defense force can't manage an intercept? they're also of no value.
Specific missions will need specific types of equipment and specific operational doctrines. An antipiracy force will tend to be mobile, and operate in small numbers against less well equipped pirate-raider type foes, they'll lean heavily on the scout role and survey work, and because of the nature of the mission, they're going to be 'out' quite often, requiring dedicated logistics. An invasion focused navy will tend to lean toward 'heavy' ships both for logistics, and because they're going to be deliberately going up against peer forces.
a 'defensive' fleet needs to be as mobile as an antipiracy fleet, and more-because to be of any use, you have to get your defending units to where the attacker is arriving, and you have to be heavy enough to turn, delay, or destroy them. what they do NOT need, is the same jump
range as an antipiracy fleet. Defensive fleet units kinda need to be able to manage preplotted jump points within their system, whether to get the dropships in range before the enemy lands, or to get the shipboard guns in range before the enemy gets reinforcements. Dropships are, then, 'cargo'-they're the payload, not the means of delivering it. Same with fighters, because if the other side gets boots on the ground in large numbers you've failed, if they gain any sort of superiority in orbit, you've failed.