Im kind of surprised that Taiwan has never pursued a nuclear arsenal. They have the resources and technology to do so. A few nukes is going to be more of a deterrent than any number of reservists. The past few decades has shown that the greater powers of the world have no problem squashing you — unless you possess nuclear weapons.
Taiwan did have secret nuclear weapons program in the 70s or 80s, with cover from their nascent nuclear power facilities. When the US caught wind they forced Taiwan to shut the program down. I'm not sure if China knew about it at the time, but I imagine these days it would be impossible to keep it secret from China--too many spies.
TW/ROC was/is still thoroughly infiltrated by PRC intelligence, if there's credible hint they're moving from nuclear latency/threshold to actual nuclearization (PRC redline), the relevant facilities would be destroyed - no need for PLA boots on ground or telescoped build up, every inch of TW is within 10 minute strike of mainland based ordnances. TW nuclear turnkey potential isn't as fast as PLA rockets/bunker busters.
Unmentioned aspect of US axing TW nuclear program in late 80s, was CSIST / INER (Taiwan nuclear program) was already monitored by PRC intelligence and post Nixon normalization US intel cooperated with PRC intel to shut the program down.
Unwritten between the line is PRC, having closely monitored TW program would have probably nuked TW first if US didn't compel TW to end the program. US Inspection / IAEA went in the dismantle the program, no doubt verified by PRC intelligence, it's unlikely TW can rebuild to nuclear turnkey faster than PRC can mount an invasion. And realistically TW can't fend off a PRC invasion without US involvement, and if US involves to assist TW nuclearizing then TW going to get nuked, and US + PRC will stare down MAD.
Also note PRC fought as in actually shed blood with USSR, India (both borderm skirmishes), US+NATO in Korea, armed Viet against FR, threatened UK over HK... aka every NPT nuclear state over sovereignty/security issues much less important than TW. A few of them when PRC had no/barely any nukes herself. Nuclear simply has never been a credible threat against PRC soverignty issues.