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.
Invasion maybe.
I think if I was in charge of strategic policy at TW I would get as close to a nuke as I could without raising suspicions in the PRC and then once the PRC gets involved in a war or domestic turmoil I would rush to nukes as fast as possible.
If TW could nuclearize without PRC (or US) knowing, they would have already. But I don't think they can, and despite the occasional US hawks thinks it's neat idea to put TW under US nuclear umbrella, sane planners they know PRC will attribute TW nuclearizing to US negligence (really participation) since unlikely TW can do so without PRC notice unless US help obfuscate. Trying to hide being near threshold while waiting for PRC collapse and assume PRC won't/can't find out even less likely. In which case that's a Cuban crisis PRC won't flinch from, and TW nuclear use will be equivicated with US nuclear use. It's not the galaxy brain one simple trick people think it is. As PRC builds up nuke parity with US, this idea going to be extra bad.
Somewhat related, domestic politics aside, one has to wonder if other forces behind why TW is decommissioning her nuclear plants and becoming even more energy dependant, and less nuclear latent.
IMO US global war experience doesn't amount to much relevant in peer war, in peers backyard, against peer whos spend last 20 years soley fixated on countering US. IMO most don't realize how meagre current USN (and general US posture) is in IndoPac relative to current PRC size and what PRC has in threatre (everything), and how extra meagre 7th fleet in indopac is, CVN76 (carrier group) + desron15 (destroyer squadron) is like 10-20 ships depending on deployment. Last few years PRC coast guard messing around in Senkakus, dozens of incidents every year that should on paper trigger US defense obligation, but nothing from US. USN hasn't been credible deterrent for a while. US not sending carriers through TW straight for years, current US planning has carriers operate out of PRC backyard during shooting war to hopefully figure out way to do standoff strikes. Assuming they're not sunk before that. Or assuming they can operate more than a few days since PRC missiles can hit most replenishment sites/fleets. For reference invading 90s Iraq took 5 carriers group + regional basing + french selling out Iraqi air defense. Eisenhower carrier / CVN69+DDGs aren't exactly defeating houthis right now. Current PRC is like 80x larger than Iraq then by population, 100x larger by gdp, and 100x+ more industrial output. Current one year PRC ship building is outputting cumulative US 5 year WW2 which is proxy indicator for other domains (like munitions). USN formidable against PLA 10-15 years ago, but that's also how long PRC took to close gap which they are likely to extend.
Ask how much can PRC arm Mexico, Caribbeans etc to prevent US from destroying Cuba if US really wanted to. The reasonable answer is no amount, the proposition is borderline stupid because the force balance size between US vs rest is just that lopsided. Same force balance trend in PRC vs US+co in IndoPac now. PLA growing/modernizing faster than everyone else combined, US containment partners who can't comtain are now liabilities - US still obligated to defend in PRC unfavourable ground of PRC backyard.
Trend of geopolitics indicate US allies are less than ready, and outside of theatrics, has signalled _zero_ actual formal commitment. SKR opposition drafting legistlation to prevent SKR from assisting US in TW scenario a few weeks ago. JP avoid openning up main islands for expanded US basing despite US asking for ~10 years now. All those "war games" propaganda that US can win in variety of scenarios against PRC... depends on those expanded basing (and a bunch of PLA hardware not working). Current US posture (again without expanded basing) is not sufficient. PH is more or less irrelevant. What can India do on other side of Himalayas?
Hence current US military posture (which includes allies) is not sufficient, because allies have repeatedly demonstrated through action & inaction that they are extremely unwilling to seriously help US for TW, because as import dependant islands they don't want to be PRC missile sinks, and regress into developing countries if PRC decides to do their own "operation starvation". And when PLA occasionally do leaks like cruise missile gigafactory that makes 1000 components a day i.e. a few days production will satuate all US interceptors in 1IC, every year it becomes increasingly obvious US can't prepoposition enough hardware to shift balance vs PRC, not just TW in scenario, questionable if US even able defend JP, SKR, PH etc.
isis-online.org/uploads/isis-reports/documents/TaiwansFormerNuclearWeaponsProgram_POD_color_withCover.pdf
Looks like there are some old archived articles on TW wiki of their nuclear program. Coverage stirried up in early 2000s when US/PRC relations warming up and TW felt threatened about their security started seeding more info about nuclear program, hinting they can restart. I read some of the books that started popping up a few years later, they were in Chinese, I can't recall them anymore.
https://zh.wikipedia.org/wiki/%E4%B8%AD%E8%8F%AF%E6%B0%91%E5...
ISIS report interesting in that on the box on page 123, note 14, acknowledges US+PRC intelligence cooperation (from interview by authors with former CIA/US ambassador to PRC). This is something I've seen mentioned in Chinese writing years ago, getting confirmed. Hence there's something to PRC's narrative that they had foreknowledge of TW program and had hand in compelling US to dismantle TW nuclear program to avert crisis.