I think it would be far more cost-effective to upgrade the FCR's rather than upgrading the missile seekers of every individual HQ-16 in the PLAN inventory. The current Orekh/MR-90 clone is probably PESA like its progenitor. Redesigning it into an AESA and boosting its range would give it the ability to illuminate multiple simultaneous engagements at much longer distances. It would be a massive force multiplier for the 054A. The range of the SPG-62 that the USN uses to provide terminal illumination for SM-2's has a range of something like 200km, so I know the MR-90 can do better than it does now. If the PLAN get a redesigned MR-90 to irradiate out to anywhere near that range, we could potentially even see the PLAN start to experiment with booster rockets for its HQ-16's, assuming its associated VLS could handle the additional length. That would be a sight to see.
Taking this thought process a step further, you could mount 4 fixed AESA panels high on the main mast to give them more OTH capability. That way you could also get rid of the Type 347 gun control radar for the main gun and just timeshare the front-facing AESA panel, as well as the Type 364 surface search radar mounted on the smokestacks. Then move the Top Plate or another volume search radar down to that location. What you would be left with are just the AESA's for surface search and gun/missile fire control, the Top Plate for volume search, and the Mineral-E for OTH AShM targeting. Less cluttered design, and it may save some top weight on the ship.