F-16V and F-35
Articles I've seen on this Taiwan are split. Some are saying ROCAF supposedly got a bargain, ~120 mil/plane, vs. 150 mil for the other countries such as Morocco. Others are comparing to the lower price of 80 mil/F-35. One issue with the 80 mil quoted F-35 price is that most of the countries buying F-35 now previously paid Lockheed the R&D cost/corruption fees involved in the original JSF proposal. As of now, we don't know the true cost of F-35 to a non partner.
I definitely agree with the idea that the primary reason why there is no sale of F-35 to Taiwan is primarily cost related. I would say a very close second is espionage. Morale of ROC armed forces for the last 20 years has been very low. The failing transition to a volunteer force has probably made this worse. There are always regular reports of arrests of officers trying to make contact with PRC. These are the ones we actually hear about, who knows what slips through? The officer corps is probably especially vulnerable to infiltration. Oftentimes officers' motivation to make a military career has some family history involved. For Taiwan, this means KMT and thus Chinese Nationalism is a big part. If they feel the Taiwanese government is moving away from this ideal, then their loyalty will move towards the PRC. Combine this with basic bribery, and who knows what could be lost?
Production schedules, possible shootdowns, angering PRC, all of this is pretty notional (to me at least). Scheduling, if there is a need, or a desire to do it, it will happen. Divert some from USAF/USN production, why not? Shootdowns, there are no flyovers by ROCAF anymore. Angering PRC, they will get angry even if you just sell hot dogs to ROC, so what? Thus it leaves the two issues above.
Reserve system
This doesn't really make sense. Why would you need to only reform training scheduling for older people? Typical window dressing. Taiwan requires comprehensive reform of the reserve system. It is totally broken. If the top brass is projecting a need for 250K personnel, you will never be able to fill this without conscription. The total population of the whole island is just around 23 million something similar to Canada, who's total military personnel is under 100,000. In Canada, they throw a lot of money to join, even for Reservists. If you need to serve full time for 2 years, good luck, it will never happen. They need to come up with some kind of system that works around going to school and maybe guaranteed x years private sector employment, these are probably the biggest impediments.