IMO the most reliable solution for ECM of any kind is just improving ECCM.
And I have to say this entire discussion about towed decoys is really missing the forest for the trees when it comes to the air power balance across the strait. The way I see it there are four major trends or factors that are either moving in a direction that is no longer favouring Taiwan or which exist in a manner which there is no physical way of altering.
1: strategic depth. China has a lot of it, Taiwan has virtually none. The ability to have command/control centers, logistics centers and bases and so on that exists beyond the immediate "battle space" or "front" allows you to more easily sustain the battle compared to if all of those centers and bases existed within the "battle space" because it means those centers and bases will be subject to direct and convenient attack. This is simply a reflection of geography, where the area of mainland China and the area of Taiwan is very different and where the proximity between the two means the entirety of Taiwan can come under the coverage of easily redeployable mobile ground based missile and cruise missile systems as well as redeployable standoff aerial strike systems. For the PLA OTOH, only the provinces in the immediate vicinity of Taiwan will be subject to significant threat of strikes if they even happen in the first place. Furthermore it goes without saying that the difference in surface area presents very different targeting and ISR requirements for attackers, and having more surface area obviously means the defender has much more space to disperse military assets if need be (again, relevant to targeting/ISR and thus survivability).
2: qualitative and quantitative combat capability. Twenty years ago the ROCAF had a clear technological advantage in its major combat aircraft and its support aircraft that lended its forces a clear and significant qualitative advantage in combat aircraft and overall combat capability. That qualitative advantage has basically all but disappeared now and for the PLA it has resulted in a quantitative advantage while catching up in qualitative domains as well (when looking at numbers of 4, 4+ aircraft and even burgeoning 5th gen aircraft between both sides). If anything the qualitative advantage has already shifted in the PLA's favour and is likely to accelerate in coming years unless Taiwan somehow manages to procure an operationally useful number of stealth fighters of its own, but even that will not alleviate the effects of the next factor very much...
3: offensive counter air. OCA is defined as the operations made to suppress an enemy's air power, usually through the means of striking at the facilities on the ground that support air operations (bases, logistics, command/control, runways, or even fighters on the ground themselves). Both the PLA and ROC military have capabilities that could be defined as "OCA" and both sides also have various defenses that could be used to mitigate the other side's strike weapons. However the quantitative and qualitative balance of offensive capability and defensive capability are both heavily in the PLA's favour. More importantly, the aforementioned lack of strategic depth that Taiwan suffers means the entirety of Taiwan will be under the umbrella of the PLA's OCA operations whereas only parts of the Chinese mainland will experience any ROC attempts at OCA. The direct effect of OCA is to reduce the sortie rate and/or sortie effectiveness, because your fighters are unable to take off either because their runways are cratered or they have to deploy at highway strip FARPs that are less efficient than air bases or because their logistics backbone has been crippled, or because your fighters that were in the air were forced to ditch because they couldn't land at an air base, or because the fighters themselves no longer exist.
4: force multipliers/situational awareness. Finally, while this factor relates to no. 2 quite a bit, it is such a significant disparity and has historically proven to yield such a difference in successful air operations that it cannot really be ignored. The difference between ROCAF and PLA AEW&C capability and ECM/EW capability is massive. The ROCAF operates 6 E-2Ks and no dedicated ECM/EW aircraft of note (a couple of ELINT C-130s and P-3s with ELINT as well, but that's it). The PLA by last count has 4 KJ-2000s in service, 11 KJ-200s, at least 10 KJ-500s (probably more by now) for AEW&C all of which are much larger and modern than E-2Ks as well as about two dozen special mission Y-8/9 platforms split between ELINT/SIGINT, standoff ECM, across different configurations and generations. The survivability of each side's AEW&C and EW and SIGINT birds is of course fundamentally related to strategic depth and OCA as well -- the side with more strategic depth and less risk of suffering from OCA will obviously have much superior overall situational awareness, battle management and C2, compared to the side which lacks strategic depth and at much higher risk of suffering from OCA.
This isn't to say the ROCAF have no chance to exact a degree of cost vs the PLA in event of a conflict if it ever happens.
But I do think it means the balance of overall air power capability between the two sides is such that it is worst it has ever been for the ROCAF and is likely to accelerate in that direction further in coming years rather than move in the opposing way.
