Let me put it this way.
054B is noticeably larger than 054A, but has the same amount of armament. The original thought that I had for 054B is that it needs to have a new propulsion to sustain faster speed than 054A (go at 29 knots) and more important to provide the cabin spacing and such needed for long deployment. And given the larger size, that like means it is designed with more cabin comfort in mind. So, you have a larger platform but without more firepower. It doesn't make sense to have a platform like this if it isn't equipped with a more powerful propulsion that can allow for future upgrades in power consumption. So, what is exactly the point?
Why don't you just build more 054A if you need more number? If you don't need more frigates right away, then why not wait for a couple of more years for when your 9.5 MW diesel engine and IEPS tech + latest high discharge battery pack tech become ready?
I look at FREMM, it uses CODLAG with 32MW GT+ 4 2.2MW diesel engine. So, just 40-41MW combined power. if you have 36-38MW pure diesel IEPS with battery storage, that is actually plenty of power for probably 29 knots and you can sustain several MW for sensors and weapons.
(1)Armament of 054A is generally enough for a frigate. Problem isn't armament, problem is sensors which guide it. Displacement visibly went into giving more sensors.
(2)Smaller ships are almost unavoidably cramped. This doesn't necessarily mean living quarters are bad(though later ships tend to offer more, arrange them more conveniently, and so on). but it almost guarantees space around functional systems is bad. This means, for instance, that not only said systems are harder to service at sea, but also it means that fixing even relatively solvable issues may require drydock.
(3)There's also always practical experience of weapon employment or sensor use(. It isn't about just armament - it's also about what seastate it can be used at, and then more and more specific nuances - sea is a tough mistress, and in general - displacement is the currency used to please her.
(4)054A is generally going towards obsolecence. Don't get me wrong - it has all the right hard capabilities(those are generally established almost 50 years ago). The problem is not what explodes, but what guides whatever explodes.
It's radar suit is generally 2000s, even with new better(but still rather small) targeting arrays. Main ship radar is type 382, which is, maybe an updated, but late 1980s Soviet design at its core - and not even top line one at that.
How does this capability works v. modern air threats? We saw infinite number of times now, how Buks, Khordads and other broadly related SAMs fail to spot modern threats and get destroyed. We even saw how Grigorovich class frigates (half sisters to 054A, btw) were...no, not hit, but just barely avoided damage, or were splashed, and as a result retired into protected harbors. 382 and HHQ-16 are not especially different.
Perhaps 054A has spherical EODAS with full merged display in CIC, like is becoming good standard nowadays(like sudden drone ambush anyone)? No, it doesn't even has a fully integrated BMS in Aegis sense.
Perhaps we want non-notional and actually deterring ASW capability? First, larger hull will outright tow larger things(like, VDS/TDS) better, at worse sea states, while suffering less hull stress and wear. Then it would be nice to have our diesels rafted. It is a major change, and if you do it seriously enough - it may seriously make submarine reconsider its life choices, as well as significantly improve your own listening capability(digital filtering of own parasitic sounds is not the same as just not being noisy in the first place). But it's new hull, and, of course, displacement. You may of course not, but then just be ready that you and your convoy will get sunk from "should've been safe" radius.
(5)ships can sustain power and cruise, it isn't like you're chosing where to rerout power a-la star wars. The problem is how you do it - different ships, per their roles, are built for different roles. Diesel ships cruise well at moderate speeds, diesel ships still can achieve high speeds, no problem. The question is for how long, and how truly combat capable ship is while diesels go full throttle. Powerful longterm vibration is nice for a certain kind of toys, not for electronics nor the crews.
And all of it is displacement, displacement, displacement. 054a wasn't armed any less than now dead Constellation, and against older/simpler threats it is more or less an equal to her. Against more modern threats(and it fully applies to rear areas as well), it isn't one, at all.
