(errr
I spent an hour working on a reply and the stupid system logged me off and I lost the whole thing so - sum-up: )
Oh man, I hate it when that happens. I've taken to writing my posts in a text document, then copy/pasting it into the submission box, because of the number of times on various forums I have had a browser crash as I was hitting submit lol. I definitely feel your pain.
hadn't heard of SCCs before, never saw them in a book.
In case you haven't seen them yet since the time you posted this, they are in Tactical Operations, on page 410-411 for stats, and page 343-344 for rules. SCC stands for Sub-Capital Cannon, there are also Sub-Capital Lasers (SCL), and four types of Sub-Capital Missiles, on the same pages. They are what allowed for the pocket warships (anti-warship DropShips essentially) in later eras, culminating in ships like the Castrum.
AMS predates the exodus (20th century tech) - the particular model found in the 2750 TRO dates back to 2617 not all of them.
While I am aware that our real life modern navies use the equivalent of AMS, unless it is something I am specifically changing for my AU, I am inclined to stick with it's introduction date in the game. Exceptions apply if there is fluff in game that could justify it, for example my use of SCCs on this ship. Techmanual lists that as 2617. For the record I treat physics the same way, ignoring real physics in favor of game rule, unless it is something I am specifically changing for the whole AU. With my ship being dated as 2117, predating even the Star League, I feel fine leaving them as machine guns. It is intentionally low-tech.
(don't know anywhere that allows them to act as AMS - that's what AMS is for.)
I can help with that:
Advanced Point Defense rules on page 96 of Strategic Operations, goes into how to use them and other similar weapons as point defense. The Aerospace Class Weapons Table on page 352 of Techmanual lists which weapons can be used as point defense (the table is specifically called out in the SO reference I gave).
For the Inner Sphere AMS, Small Lasers, Small Pulse Lasers, all Flamers, and standard or Heavy Machine Guns can all be used as point defense. For the Clans, AMS, Micro Pulse Lasers, all Flamers, standard and Heavy Machine Guns, and AP Gauss. Tactical Operations adds Laser AMS to both of those lists. Though if I remember correctly vehicular flamers can't actually be put on aerospace stuff, still there is the Heavy and ER flamers from Tactical Operations, in addition to standard ones.
If you go over the advanced point defense rules, you find that though they can be used to shoot down missiles, AMS/LAMS are vastly superior to anything else one might use that way. One of the reasons I am sticking with machine guns despite that, is that not only are other ships built between this ship's introduction and the AMS's in-game introduction using a similar set-up, but I also wanted it to be obviously low tech. I wanted someone who looks at it from a 3080 perspective to be thoroughly unimpressed. It is a Primitive JumpShip after all. It was built only 7 years after the very first primitive JumpShips were introduced (according to Interstellar Operations table in the primitive JumpShip section).
Yamato was 64,000tn when built, her mass increased with modifications to over 72,000tn, no reason it wouldn't change further, replacing oil boilers and screws with fusion thrusters, so no reason not to increase to needed level (perhaps 100-120 KTn) also 'special ship' so use vehicle turret rules +10% for RBS-Nose-LBS and RBS-Aft-LBS.
upgrade LSCCs to MSCCs in turrets, replace AC-20s with triple LSCCs in turrets (the 15.5cm) for & aft, replace all other ACs with 12xLB-10X per side and add 4 AMS, 2 each side (in-place of 13mm) though I think the MGs are useless (don't know anywhere that allows them to act as AMS - that's what AMS is for.)
personally I think you should go with Musashi, sank in the Philippians without a complete upgrade, restore her to 9xM-SCC, 12xL-SCC (3 each F/A/R/L in turrets) 6xLB-10X each side (or 2 each RB/RBS/RA/LB/LBS/LA), 64xAMS scattered, and 4xMGs @ around 100-120 KTn.
I dislike making up rules, even for my AU, so personally, I won't be putting turrets on space ships. My reason for this is wanting the largest number of people possible to be able to use units I design, and if I have screwed with the rules and the design isn't legal, that cuts out a large chunk of people who might otherwise get drawn in.
Some of the units in Project Yamato do increase in weight past their origins, but mostly only if I need to in order to fit the things I want to on them. It might be a while before I get to it, but I do have an idea to use the specs you suggest here. They won't be applied to the original Yamato, as I have already had the Word of Blake butcher that, but something will come.
I might be able to work in a Project Yamato 2.0, where I start resurrecting various other ships from Terra's ocean floor, into black water ships. It's a decent idea, and I can already see where I would fit it into the AU, so the Musashi might happen. The Yamato was picked as much as a nod to the anime as anything. Later on I'll even be adding in my own conversion of the space battleship Yamato and the Andromeda battleship that came after.
If you feel inclined to actually go through the whole design process for any of earth's modern blue water ships, into modern BattleTech black water ships, feel free and send them to me. If I need any revision to one I'll discuss it with you, then as soon as I have brought this thread to it's finish and am ready to start 2.0, I'll post them with credit and the fluff I have for them.
If you need design aids for warships that are more current than heavy metal, I do have a spreadsheet on google sheets that I have worked most of the kinks out of. Dragon Cat has been extremely helpful in troubleshooting. If you are interested, you can get the link, and instructions on how to use it here:
https://www.ourbattletech.com/forum/index.php?topic=3227.0 Sadly though, this won't help with any primitive/retrotech ships, just modern Warships with compact or sub-compact K-F drives.