Quite agreed.
There is no American solution[]
The last diesel submarine the US built was prior 1959. We are heading to 2008.
The nuclear submarine faction in the USN has sworn the US will never build, buy nor ever field a diesel sub again, not for anyone. In the past, countries like South Korea, Israel, Australia and Greece has made a request to the US to buy diesel submarines. They all went somewhere else ultimately.
There is one solution, and ultimately one solution only to Taiwan's armaments deficiencies, and that is simply to take the pain to become as self-sufficient as possible. And that means making very difficult decisions as to where to
dedicate (not merely
allocate), what resources are available to the most necessary armaments: AIP subs, ASW weapons and equipment, fighters, missiles of various descriptions, tanks, artillery/ADA, etc., prioritizing as necessary and providing resources to the extent possible. That may mean developing a domestic submarine-construction capacity while foregoing the same for tanks; the former is more critical than the latter, which may be cheaper and more efficient to procure externally until such time as resources may become available fo those too.
But it is important to point out that for any of this to have born fruit by now, Taiwan would have had to have engaged in this no later than the 1980's, when it was clear that no replacement subs would be forthcoming from the US and Taiwan's other procurement options were steadily being eroded by PRC diplomacy. That said, if Taiwan truly does want to survive, it has no option but to shake itself out of its lethargy and pour substantial, precious resources on a permanent basis into its armaments industry. If the will to survive is seriously lacking, then it will fail to do so and it will be passed by.
Perhaps the single-most powerful demonstration of its determination to persevere would be to take the pain and embark on a forthright national project for constructing its own submarines. Taiwan is not bound to succeed, but it is bound to try.