Deleting some of the ASW capabilities that are currently present on 052D would create a clearer conceptual distinction between the medium destroyer and both the large frigate and Type 055/A. Essentially, both the medium destroyer/larger frigate would offer a subset of the capabilities of 055. Or to put it another way, 055/A offers the capabilities of both new types in a single, significantly larger and more expensive ship. So that is the conceptual case, but whether or not a greater level of specialisation between types is actually sensible depends on the finer details. The savings from building each unit of each type would have to outweigh both any degradation in capability and flexibility from 055. I grant that it is not clear that it would. Although on the subject of VDS as an example of something that could hypothetically be cut from a future medium AAW destroyer, it is not merely about how much the system costs and how much volume it occupies, but the crew required to operate and maintain the system and their accommodation, dietary, exercise requirements.
I'm not convinced there needs to be a future medium destroyer rather than just running off 055s and large frigates. But if there is to be such a destroyer, the burden is on adequately distinguishing it from 055 while simultaneously generating significant cost savings and therefore greater numbers. Honestly, I would even consider eliminating the helo from such a vessel entirely, akin to Flight I Burke as a cheaper complement to Tico and alongside Spruance as the large ASW frigate with two helos.
That all sounds very sensible and I have previously advocated for a vessel of this nature to succeed 056. Though I would consider using UVLS instead and allocating a few cells for the quad-pack 5-5-5 SAM.
There is no doubt that 052D offers more "bang per ton" than most vessels of similar size and that has to come from somewhere. I would not be at all surprised if it comes out of both endurance and accommodations. And that's one of the reasons I don't see increasing the magazine size as a significant priority: the design is already densely packed as is, and if you make it much larger you undermine the rationale for its existence as a smaller/more affordable complement to 055.
I would think that the PLAN is freaked about enemy submarine capabilities that they would throw a large effort on it in the last decade. At the time when the 052D was introduced, there aren't a lot of warships in the world that has a VDS. They made an effort to switch the 054A production line to VDS, and did the same on the 056. In fact one of the primary changes between the 054A and 056A blocks have been the VDS. The VDS itself isn't something that's expensive, huge and inconvenient to add on --- all it needs is a port on the back with a long reel. Comparative to the previous world standard of hull sonar and TAS, VDS allows you to penetrate and listen through different thermal layers. Hull sonar and TAS can be beaten by a submarine who knows how to use thermal and salinity layers which can deflect sound. Helicopters with dipping sonars have a disadvantage because of their limited endurance. TAS is dependent on how quiet and noisy a submarine as TAS are passive sonars. But a ship with a VDS can probe any depth any layer for any length of time, and because its active -- ping ping ping --- it does not matter how quiet you are --- the sub is going to echo back those pings. Kudos for the PLAN for decisively quick fitting its ships with VDS, when other navies are dragging their feet on this issue for budgetary and bureaucratic reasons.
With regards to the 056A followup - 2500 ton ASW light frigate, I can choose a U-VLS as long as U-VLS has an ASROC option. I am not referring to the YU-8 fitting on the U-VLS, the YU-8 is well undersized for it and its quite a waste of space. The U-VLS should have an ASROC that makes better use of its space, and that means a missile-torpedo that's going to be larger than the YU-8, which means greater range or so on, like a YU-7 torpedo attached to the YJ-18's cruise body.
Given the size of the vessel, an 8 cell U-VLS is the option with 8 ASROCs. Using the 3-5 missile with it would likely mean a change in missile configuration, reducing the ASROCs for the air defense, but most importantly a change in the vessel's radar setup which in turn raises the cost of the vessel. At the minimum, the 3-5 missile, which I expect to be active guided, would need supplementary midphase updates from the radar and needs a radar capable of accurate updates. The HQ-10 on the other hand is a passive/IR missile ---- it locks to the target's heat and is a heat seeking missile. Against other aircraft, it would have to be protected by another vessel like the heavy frigate or light destroyer but at least it should be able to protect itself at close ranges.
Going back to the short list of ASW specialized modern warships, like the Type 22, Type 23 frigates and the Udaloy class destroyers, they are equipped with mainly short range missiles. The Udaloy is equipped with Kinzhals in rotary VLS, which amounts to a naval Tor-M1 or HQ-17. The primary weapon of the Udaloy is a huge ASROC that's code named Silex, which is like a cruise missile with a torpedo attached to it, and that's what fills up those large missile canisters the type is visually known for.