Ok, let me see if I have this right. Take a 9MT SD(P) and remove the (P), because you don't survive an Alpha Strike from a pod layer anyways and why carry pods that will never be used. This means you are building a DN, with the same SD hardware in a smaller package, that will limpet pods to the sides of the ship for use in battle. The scaled down DN, lets call it the Hood class, will have ammo supply integrated with the fleet for the DN to re-limpet pods to the sides for the next engagement, ala Terekhov's Squadron at Monica. This way you can build them cheaper and faster and have more of them, right?
So, here are my issues with that plan.
-----FIRST-----
Putting in the hardware in place. So here is our SD(P).
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Remove the pods and our new Hood class DN follows.
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Works fine for the internal hardware as that is already moveable within accepted constraints from class to class. (The fusion reactors are deep in the hull to better protect vs golden BBs taking out the fusion reactor and the like.)
Now the problem you have, is that weapons, sensors, keyhole platforms, etc are spread across the outside of the hull.
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So above is our SD again and all that juicy tonnage for offensive fire control links and defensive fire control links and sensors and weapons have all that surface area to fit in stuff, unlike our new Hood class DN below, which lost surface area to fit in stuff by because it is smaller.
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-----SECOND-----
Ammo storage. So lets replay the Battle of Monica with our new Hood Class DNs and upgrade the other side as well. So now we are attacking Monica to keep them from deploying SDs against us. (CA to DN as BC to SD to keep everything relatively equal.) The first part of the engagement to take out the shipyards goes well. Use them or loose them alpha strike with pods and all that like always with limpet-ed pods. But vs SDs stealthly attacking on another vector, you have a problem. Your ammo ship is outside the limit since it is unarmored and you are not. Well, we will get them when they get into grazer range as that is all we have left.
So, lets armor up our ammo ships so they can follow the Hood class DNs into battle. Well to make them survivable enough to tag along, we need to give them DN/SD armor. And you know, with some fire control links, they could do the job themselves and we wouldn't need the Hood class at all as we have built a SD(P).
Don't think that Monica is a one off either. At Solon, Duchess Harrington was attacked by Adm Giscard and then had to squeeze by Rear Adm Emile Deutscher's force who was in system that Duchess Harrington was able to see, before the ambushers showed up. Once again, the use it or lose it vs Adm Giscard would have meant nothing to shoot at Rear Adm Deutscher's force.
-----THIRD-----
Why hamstring your fleet commanders that way by having the wall of battle carry around ammo ships everywhere you go? Let's say you armored up the ammo ship to have it travel along with the squadron wall of battle. So each wall could be 6 DNs and 2 Ammo ships per squadron to keep the 6 wallers per squadron scenario that the RMN has now. If out of those 8 ships, one is down for mobility from damage or engineering casualty or required maintenance, that would not be an unlikely scenario for warships. If it is one of your two Ammo ships, you lose half of your ammo for the whole squadron AND the 6 DNs are stuck to the Ammo ship like a hungry baby to mama. With 6 SD(P)s, having one down means losing 1/6 the ammo for the whole squadron and you can still break up the other 5 with other wallers or by themselves as needed. Even with out mobility issues, if you want to breakup your DN squadron, you would have to send 3 DNs and one Ammo ship out at a time, so you would be able break up your quadron in two, where the SD(P)s can be broken up into as many as 6 units. You can go with more ammo ships per squadron, but then you are adding to crews needed and more ships you have to build.
And along with this, why have a squadron of wallers that can be rendered into nothing more than targets by taking out only 1/4 of the wallers in said squadron? Are you secretly yearning for the Weapon That Can Not Be Named? Because if you had DNs and ammo ships, this would be the perfect reason to bring it back to the detriment of CL captains everywhere. Take out the Ammo ships and the other six DNs are targets.
-----FOURTH-----
Making the Fifth Space Lord resign. I get this from RFCs post archived on Pearls of Weber titled
The return of battleships as a viable class; the info on crews is listed as "Sixth" near the bottom of the post. Per RFC, the manpower requirement for a BB was nearly the same as a SD. So I doubt a DN would be very different than a SD. So with a squadron of 6 SD(P)s you need 6 waller crews. With your squadron of DNs, you need the same 6 waller crews, plus the crews of the ammo ships. So, you are not saving but adding to the manpower requirements for your fleet and Adm Cortez is having enough trouble finding crews for the wallers and the screen as it is. He already had the jump in manpower problems with the LACs and now you would be adding even more critical ships to crew as without the Ammo ships, your DNs are nothing more than very expensive targets. Yes, the Ammo ships would not have a very big crew if you unarmored them as they are freighters. If you armored them, then the crew requirements go up, as you need damage control to keep it running in combat and afterward.
-----FIFTH-----
Don't forget that the fleet doesn't exist in a vacuum and politics will come into play. If you don't armor your ammo ships, but they have to tag along with the DNs, morale (both civilian and military) goes in the crapper for sending out crews in death traps. Not to mention that you are sending out the waller crews in a smaller ship rather than a bigger ship. All the juicy, necessary hardware in this;
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is a lot easier to hit than in this.
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So it will be easier to mission kill or outright kill the DN over the SD.
For more on unarmored ships see
With Apollo, do you really need armor any more? The DNs proposed above are not quite as bad as situation, but toward that direction with a waller attrition unit.
-----SIXTH-----
Lets talk about construction and costs. I get this from RFCs post archived on Pearls of Weber titled
The return of battleships as a viable class; the info on on constructions and costs are listed as "Third" and "Fourth" near the bottom of the post. Per RFC, the costs of a BB would be 2/3 to 1/2 of the costs of a SD. I'm sure the cost of building a DN would be even closer to the cost of a SD, so you
would not be saving that much by having a less capable platform that would hamstring you as listed above. If you are building more, less capable ships, you need more construction crews and this issue is
THE most problematic issue of building DNs over SD(P)s for the GA after Oyster Bay than all of the other issues combined! In "Fourth" in the above post, RFC lists a 6MT DN as 20.1 months to build and a SP(P) as 23 months to build. Not that much difference for a less capable platform especially when you have less building ways to build them in the first place.
-----SEVENTH-----
So, lets build a DN(P) and make the 20.1 months go down even further since we have so few construction ways in the first place! First, you have to design the thing and then build it. Adm Hamish Alexander discusses this in chapter 7 of At All Costs. He estimates a DN(P) would take 18 months to build once under full production, but three years to design and get it into full production. And that was when they were discussing attacking Haven just after Operation Thunderbolt when they still had all of the construction ways and production facilities. After Oyster Bay, when all of that has to be rebuilt before you can start on the DN(P)s? Not likely. Going with what is already designed and ready with the parts that were in storage that were not lost to OB, is almost certainly where they will go.
Not to mention. Remember this?
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Now you turn it into this.
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So you lose even more capability from an SD(P). But Battle Fleet has obsolete ships you say. Doesn't mean that they will stay that way. The RFC post archived on Pearls of Weber titled
The basis for Manticoran inventiveness discusses how the Manty's advantage of the Junction allows info from all over the Solarian League to be integrated into the Manty industrial complex. So, info is out there and the SL or someone else can get to where the Manty's are now. And as large as the SL is, they can get there pretty quickly. Even if it broke up into sectors, those sectors can get there pretty quickly. So why build a less capable unit, when manpower requirements of the ships is one of your biggest concerns, when the SL and others are going to be replacing the obsolete ships you want to destroy now, with better ones? And will have a bigger manufacturing ability than you as they are also larger? Before the first Havenite War, the RMN built DNs because funding was the biggest limiter on fleet size. Since then discussions about Adm Cortez trying to fill the fleet with crews, I'm almost certain that manpower is the limiting factor in the RMN now. So why build a less capable unit for your limited manpower, instead of a more capable unit when the costs or construction times are so close?