Any building with broken wall is a suitable hiding place.
So are mountain forests, caves, tunnels... everywhere with some roof/disguise v space really.
Himars is a small truck. The only real downside is again limitations of main ammo type, which only barely reaches into Fujian.
But that's the point, too, selling direct means of countervalue to Taiwan will lead to extreme detoriation of US relationship with PRC.
Ukrainian himars are regularly used v civilian targets, there's very obvious stigma on them and what they can be sold for.
HIMARS is just MLRS. Even Pakistan can produce its own ultra long range MLRS that has ATACMS ranges. It should be piece of Cake for highly industrialized Taiwan to produce it themselves.
China cannot rely on a military strategy against Taiwan that is reliant on Taiwan not having access such widely availble weapons. Things like Drones, Tactical Ballistic Missiles and Anti-Ship Missiles are now very mature technologies and can be easily produced by Taiwan if they get serious about it.
So, its actually better that US is providing these things to Taiwan at a huge mark up price rather than Taiwan being forced to produce it by themselves, which they will be able to do at a much cheaper per unit price and likely can produce hundreds if not thousands of launchers if needed.
As I have said before in this thread, China's strategy of defeating Taiwan must be overwhelming dominance. Brute force Taiwan out.
There should be overwhelming defence such that, If Taiwan is launching 100 ATACMS, China should have 500 interceptor launchers on standby to intercept them.
Overwhelming offense: China should saturate Taiwan with enough drones and satellite surveillence that every meter is under inspection and every concealed launcher gets detected after firing their first shot and then gets destroyed in minutes.
China should be infiltrating Taiwan in such a way that Mossad attack on Iran should look tame in comparison and these agents should be sabotaging Taiwanese offense and defense before day 1.
If China cannot even overwhelmingly defeat 22 million population Taiwan with 1.4 billion people, they should be ashamed of their weakness. If there is indeed a war, they should utterly wipe the floor against Taiwan in such a way that Desert Storm looks tough in comparison. China should not even try to initiate the war until they get that level of dominance.
China should have enough dominance even if US bankrupts itself by providing Taiwan its entire stockpile, Taiwan will still lose.