I think it keeps a 1:1 ratio when the YJ-12 replaces the YJ-83. You often see the refitted 167 with 8 YJ-12s, but in fact it can still carry 16. Very likely the 054A/P can carry up to 8.(1)YJ-83/YJ-12 aren't plug-and-play, like, say, Taiwanese ones. It's possible to change them through modernization(1 for 2 at that), of course, but it is an exchange of capability set(i.e. sidegrade).
(2)For multi-purpose frigate YJ-83s make more sense(they're more numerous per unit of weight, more universal, and more usable). Bigger =/= better. YJ-83 is likely to be enough for everything you're likely to get a shot at within 1st Chain. Large supersonic missiles aren't overly suitable to engage smaller targets, for example - and you're getting fewer on 054AP.
(3)you already have several much larger platforms at your disposal, - with already established crews, with 1-2 decades of designed life left, and which were originally meant to do just that(and carry 8-16 heavy missiles from day 1 anyways).
All the advantages, no disadvantages.