After cross referencing in service dates for all the ships in the master ship tables of SFB Commander's Edition, it transpires that SFC year 0 is actually 2246 and not the rounded up 2250 reckoned on in the game.
The Lancaster class cruiser we already have in the "library" for LAN games here plus the Al Burak class carrier, though these were probally in Star Fleet service during the 4 years war.
The Hyperion was also a cruiser though more geared towards replacing the Daedalus class in exploration than as a warship.
We also have tried out fighting skirmishes from the Romulan war using the various models based on the Star Fleet Museum pictures. Apart from the fact that nobody has made a model of the Romulan Cabbage class starship, lets just say that battles happen at a more pedestrian pace, lots of slow moving Drone A missiles flying everywhere and shields, if your ship is lucky to have any, are so weak that they simply reduce the amount of damage incured from a hit. Formation firepower seems to be the main tactic.
Federation limited to Phaser 3, Drone A, Disrupter 1 (substitute for Particla Beam Cannons). Defences are Radio Polarised Hull Plates (Shield 1 all around) or Shields up to 5 points all around).
Romulans limited to Plasma F, Disrupter 1 (2 later), Drone A. Defences Ablative Armour and good ECM. Also long range sensor deception and maskerade (using LOD 2 and LOD 3 on models in the game).
We've also tried out skirmishes in the post Earth - Romulan War period between the other neighbouring races of the Romulans. The Klingon annexation war, which dragged on for more than 15 years, saw a pre-anti-matter war technology Klingon Empire attempt to take advantage of a perceived defeated and weakened Romulan Imperial Empire.... which was doomed to failure as the Romulans, whilst lacking numbers, still had a technological advantage in both ships, training and weaponry.
The Klingons also relied on Neutronic and Sub Atomic Impulse powered warp technology that was, by everyone else's standards, gas guzzly and short ranged. The Klingons had to set up tanker way stations weeks and months in advance before moving warships into an area, giving advance notice to the Romulans, that trouble would be arriving.
For this Klingons had only Disrupter 1, Photon torpedoes and Drone A. Romulans Plasma F, Disrupter 2 and Drone A.
Back to the subject in hand....
The Mann class is a light cruiser so fitting a 3rd engine would only increase warp power at the increase of movement cost. It also has the same limitation for direct fire weapons though I guess some science labs coud be ripped out and replace with missile racks.
The Moskva class, generally because of its size and the number of phaser hardpoints (check out the Star Fleet Museum diagram!!) would be the most suitable basis a design for of a dreadnaught of battleship with probally a large secondary hull design but keeping the same elipsoid.
I was thinking something along the lines of the USS Iron Duke, though that is a TOS design. 4 x engines on a hull with a Moskva, Lincoln or spherical command section. That would be good for 2200 though it would probally be a unique ship. Maybe call it the Mellenium class if it was in service in time for the start of the 23rd century in 2201.
Engines, for 2220 to 2240, are probally 12 boxes in power, if one goes by the Texas Class CL, Kearsarge class NCL, Equniox, Horizon, Pytheus, etc. starships that were all commisioned during this period.
I generally allow a move penalty of 0.25 for evry warp engine added to a hull, based around the pod move cost penalty in SFB rules. We also run fleet battle tenders, which carry spare unpowered warp engines strapped to the hull for campaigns.
I formulated a system for relating the largest warp engine box maximum for Federation starships given a time period. Movement costs altered so that vessels can achieve speed 31 on full warp power, though speed drops drastically if just 1 warp box is taken out on earlier vessels. Note that possible armaments carried has to be proportional to the amount of warp power available to supply it. ( Stuffing the ship with APR isn't allowed!!)
Smaller ships of each period, such as frigates, would use a scaled down half size of engine, in warp boxes, of the largest engine available.
TNG 30 + 30 (Galaxy, Nebula, Freedom, etc.)
Pre-TNG = 30 (Ambassador, etc.)
Transwarp = 24 (Excelsior, Curnow, etc.)
TMP = 16 (Linear warp drive. Constellation class = 14 per engine)
Post TOS = 20 (X-Ships and Star Fleet's Advanced Circuferential Engine programme).
TOS = 15 (Includes SCNN Scarbak engines on the Endeavor CB).
2230 to 2245 = 14 (Asia, etc.)
2210 to 2230 = 12 (Moskva, Texas, Kearsarge, Confederation, Equinox, Horizon, Baton Rouge, Pytheus, etc.)
2190 to 2210 = 11 (Hyperion, etc.)
2170 to 2190 = 10 (Mann, etc.)
2160 to 2170 = 9 (Lincoln, etc.)
2150 to 2160 = 8 (Daedalus, Tiger, Discovery, etc.)
2140 to 2150 = 7 (NX class and Sweden class frigates, etc.)
UES Naval Fleet = 6
2070 to 2140 gradual learning curve increments as Earth masters warp drive technology.
2068 = 1
If one throws in movement penalties based on ship's total hull mass, in addition to warp engines, based on a total box count, some of the pre-Tos eras does present problems that simply cannot be solve by bolting on more engines, unless a slow but powerful warship is desired.
Similar but not identical increments could equally be applied to all the other races. For example, at what point did the Kzinti decide to go for a third engine in their design ethos??
For the Klingons there are only a few periods of warp and weapons technology. No phaser 2 before 2245 (4 years war), no phasers at all before 2200 and Disrupter 2 only from 2170, Disrupter 3 from 2200.
TNG = 30
pre-TNG = 20
2245 Late S-Graph = 15 (D6, D7, etc.)
2190 Middle S-graph = 12 (MAM powered technology D4, D5, etc.)
2150 Early S-Graph = 10 (Neutronic fueled technology. YD3, YD4, YD5, YD6, etc.)
1900's Neutronic = 5 (Also combined nachelles to give up to 8 boxes. W1 dreadnaught, Barges, some Freighters, etc.)
1800's Early Neutronic = 1 to 4 boxes.
Having seen some of the paper designs folks have cobbled together on some website, and then applied the above power available against the number of weapons bolted to the hull, on some of the TMP designs, it becomes clear that under SFB and SFC rules movement and / or charging all of the weapons would create some problems.
I've had to model some just to include into the LAN games because somebody insisted in trying it out. The USS New Hampshire is a prime example of "Didn't think it through" designing. It transpired that with only 2 x 16 boxes of warp, 2 x impulse and 2 x APR, attempting to recharge 8 x Phaser 4 turrets, plus 6 x Phaser 1's required the owning player to make distance from the battle and spend 2 or 3 minutes recharging with fingers crossed that nobody came after him. On the plus side it did slaughter a D7L in one go but was hounded so much that it never managed a chance to stop to recharge its weapons. Super Soyuz designs are always doomed to failure in battle.