Well, considering the discussion is how China should prepare for the prospect of the US frontloading the western pacific with long range strike weapons, I think those red lines had better start to be considered.
The reason I have phrased my replies as so, is that I think from the Chinese leadership's point of view, all of the politicking and diplomacy that they can try to aim to do in the future will not replace the demands for developing weapons systems and doctrine to account for the threat that is described.
Given the timescale of weapons development and force generation, it means that as of right now, the only reasonable position to take is to consider a prospect where the US has successfully frontloaded the western pacific with long range strike weapons, and to consider what types of systems and capabilities the PLA would require to achieve their geopolitical goals in that context.
Remember that if the US wants to front-load strike forces in the Western Pacific, these forces will be vulnerable to being wiped out in a surprise first strike. Plus the US is reliant on basing these forces mainly on non-US territory.
If any red lines are crossed, I expect the Chinese response would be:
1. targeted economic sanctions like we saw with the response to THAAD in Korea and the Chinese fishermen that Japan arrested. China is large enough to impose such sanctions at little cost to itself and it may even work out as a net economic positive for China if it results in more domestic production instead of imports.
2. or an increased military or paramilitary training tempo, designed to exhaust the opposing side's aircraft and ships, like we see in the Diaoyu/Senkaku Islands with Japan.
And given the prevailing view that China could become far larger than the US (from an economic and military perspective) in the coming decades, it makes more sense for countries to hedge against this scenario rather than go completely with the US and host offensive missiles and aircraft. And from the Chinese perspective, China should be content with neutrality from their neighbours because if China grows to become 3x larger than the USA and spends more on the military, there is no way that the US can maintain a credible military posture in the Western Pacific. The other thing to note is the current generation of Chinese leaders were forged through the experiences of the Cultural Revolution. But they will eventually be replaced with a softer 80s generation and then an even softer generation who grew up as millenials.
Anyway, so I expect any US long-range weapons would be confined to operating from a limited number of bases (eg. Guam, Wake Island, Alaska, Australia, Hawaii) and naval platforms. That reduces potential numbers of US offensive weapons substantially. It also increases the range requirements for US weapons to hit China and therefore the cost of such weapons.
My gut tells me the likely number of long-range US weapons, platforms and bases would be manageable for China.
The main thing would be for China to:
1. double-down on its hypersonic/ballistic missile programme targeting any US forces within the 1st and 2nd Island Chains
2. also work on systems to extend the defence perimeter to 5000-6000km from China. That would be through introducing systems like the H-20 stealth bomber, SS(G)Ns and longer-ranged missiles. That means bases in Wake, Alaska and Northern Australia are now in range. It also means the Suez Canal, Mediterranean Sea and the Baltic Sea could be covered. The Persian Gulf can already be covered with the DF-26.
3. focus on smaller, distributed weapons systems (like large numbers of simple low-cost UCAVs)