You mentioned many separate points in just a few words, my 2 cents:It isn’t throwing money away to produce more J-16s. China still needs to replace hundreds of legacy J-7/8s and J-16 is better suited for multi role operations due to larger payload. Fifth gen are also expensive to operate. Considering that among China’s neighbors, only South Korea and Japan are operating fifth gens, it isn’t economical for China to go for full fifth gen fleet. Even the U.S. is purchasing new F-15s.
1, i think we should rethink the claim of J16 being multi-role, given the fact of 5th-gen proliferation in east Asia. I don't have the exact number off the top my head but by 2030, F35 operated by US PACOM+Japan+SK would probably be in the range of 500~1000? Do we really expect J16 be able to carry out air superiority mission in such an environment by then?
2, then if China plan to use J16 primarily as a striker in high end conflict, does it provide better capability compare to J20? Well, consider the fact J20 can carry large amount of external payload, it probably can be just as good as J16 as a striker, if not better. So seriously, the real multirole aircraft here is J20.
3, some may argue J20 is more expensive and harder to maintain, first i am curious how much more expensive we are talking about? and if you consider the absolute air superiority here, J20 probably has much better cost effectiveness.
4, with regard to the replacement of older fleet or the need to keep the PLAAF at a certain size, wouldn't it be more reasonable to replace them with J10c which has a lower cost yet still effective in low-end conflict?
5, as to other theater such as southwest, do we really need more brand new 4th gen airframes just for that? After all, the current 4th gen fleet is already quite sizable and still very young.
And no, i dont think this is comparable to recent F15 order because for USAAF, majority of the purchase is on F35 now, while PLAAF seems to be still purchasing J16 (>48 yearly?) at a quite high rate and J20 at a quite low rate(<24 yearly?). If that is the case the only explanation to me is J20 still has some technical difficulties to be really mass produced, so they have no choice but to settle for the next best option - J16, in order to ramp up for short term threat, although that option is much much inferior.