In Sweden, there was a language that was considered a dialect of Swedish but actually was not understandable to those who spoke Swedish. Finally, they decided to classify it as a language and seek to preserve it. Their solution: a preschool where the language is used. And for those who attend, the language will continue to be used as a medium of instruction until the end of high school.
Taiwan's Austronesian language must have the same treatment to survive -- the language itself must be used as a medium of instruction rather than just have a class using Mandarin to teach the language.
And many of Taiwan's Austronesian languages are in even more danger than this language in Sweden, Elfdalian, which is close to Old Norse.
The language was probably able to survive so long because of the isolation of the town that spoke it. In Taiwan, ever since the Japanese forced many of the Austronesian tribes down from the mountains, they have lost that preservation that isolation brings. Further, every day brings further encroachment from non-Austronesians on Taiwan's east coast where the majority of the Austronesian peoples that still remain distinct live. These languages will not be preserved through isolation. And since the government has forced Mandarin on these peoples, the children grow up hardly speaking their mother tongue at all.
Another factor that could help the language is to pass land covenant laws where in designated Austronesian areas, land ownership can only be held by those who speak the language of the particular Austronesian tribe.