I agree that the PLA-N probably wouldn't bother making a requirement for the KJ-600 to have RATO capabilities. IIRC, the Shandong #17 wasn't part of the original plan until SecGen Xi made the request for whatever reason. It's obvious that the PLA-N wanted CATOBAR carriers from the very beginning. However, my original comment (in response to DaTang cavalry post
) was under the assumption that the KJ-600 would begin testing on their current active carriers. I believe I may have misinterpreted his comment.
But in an exercise of "what-ifs", if RATO capabilities were included in the KJ-600 design, they don't have to ignite all the rockets at the same time (i.e. staggered ignition). Once the aircraft is on the ramp then all rockets are ignited. The other method as you suggested is probably better but they first have to make some modifications on the jet blast deflectors and wheel chocks as they're all oriented towards the ramp.
According to another member here, snake65, he suggested that the Liaoning #16 was designed to have one catapult on the angled deck and his source was Valery Babich, a former Soviet engineer shipbuilder. Apparently he wrote some books but it's all in Russian and there's no electronic copy that I could find to verify it. However, there's no indication that the sister ship, Shandong #17, incorporated such capabilities assuming Babich told the truth (or snake65 misinterpreted what he read). In any case, I agree with plawolf. The PLA-N isn't going to spend resources to upgrade both the Liaoning (and possibly the Shandong) when there's going to be many "full" carriers being built in the near future, along with the Type 076 which is rumored to have a single catapult.