054 only has the AA capabilities of something like an 056? Have you thought about the combat system, sensors, close in weapon systems, the decoy launchers, extra operators and things like that?
In terms of function, the HQ7 is effectively a point defence missile the same as the HQ10. The HQ7 has more range and a bigger warhead, but they are still only going to be shooting at incoming missiles as there is no way the HQ7 can hit a fighter unless it was trying to kamikaze you.
If the 054 has a comprehansive sensor and AA battle management suit in place or has the provisions for one, than that is even more reason to upgrade the missile so those systems and sensors could be put to best use instead of being limited by the range of the HQ7.
HQ-16 is not a stand alone system. Think about the deck penetration of the HQ-16 vs HHQ-7? What would you have to change inside the ship as a result of that? I haven't seen a naval version of non-VLS HQ-16, but I'd imagine the reloaders and the weight of HQ-16 system will different from that of HHQ-7. Think about the extra sensors that accompany HQ-16 that would have to be installed on 054 and how that might affect the sea-worthiness of 054.
All good points, and all things the shipyard would have had to resolve when they developed the 054 design into the 054A. All that work had already been done, and based on the relatively short time between the 054 and 054A designs, chances as the mods were not too extensive or comprehensive. There is even the possibility that the 054 themselves were designed with VLS in mind, but had to make do with HQ7s because the HQ16 was not ready in time. If that was the case, then there is a good chance that the internal structure was designed to allow for a retrofit of VLS at a later date.
If you upgrade HQ-16, you'd have to think about upgrading the other parts of the AAW suite too. So, what structural changes would be required to replace AK-630 (which requires no deck penetration) with Type 730 (which does have deck penetration).
Why is CIWS tied to missile choice? If adding the Type 730 would require too much work, then just stick with the AKs. It's not like the choice of missile has to be tied to CISW. And funny you should being in 112 and 113, if it was possible to retrofit 730s onto them, then there really shouldn't be that big of a problem doing the same with the 054s.
On top of this, you probably have to make changes to combat system, wiring, power systems inside the ship. This is not a cheap change.
That is why I suggested the mid-life overhaul as a good time to consider this upgrade, as by that time, all the wiring and sensors would need replacing anyways.
You already have ready-made blue prints for turning 054s into 054As. Granted it will be harder to upgrade existing ships than to build the new design from scratch, but there is a pretty good chance that it can be done, especially if the original 054 design had provisions for VLS.
Even if they didn't the designers would have wanted to minimise the changes they would have had to make to the 054 design to turn them into 054As on the 'if it isn't broke, don't fix it' principle. Which increase the chances of such an upgrade being possible.
Look at all of the time 112 and 113 spent in the dry docks and it still could not even get HQ-10 installed let alone HQ-16
Well the 112 and 113 hulls were never designed with VLS in mind, and if they wanted to put in VLS, they would have had to come up with a revised design from scratch. Such a design is already readily available for the 054, and has been demonstrated as perfectly feasible by the 054A.
As for the decision to keep HQ7s, well didn't you yourself suggest that that was more for logistical reasons on account of the PLAN still having a large stock of HQ7s?
There is absolutely no technical issues that I can see that would stop the PLAN putting HQ10s on 112 an 113 in place of the HQ7s if they really wanted to.