Very interesting thought. The question is when. When the jade is discovered and when it first starts being properly exploited can potentially produce some very different results.
If it happens early enough, the extra investment might make the island defensible come the fall of the Ming. In that case, Taiwan might well never be Chinese.
After Koxinga/Koksengia/Guoxingye seized the island, it's a different matter entirely. The island will be Chinese, yet efforts by outside powers to snap it up during the Qing time of troubles will only intensify.
If it comes under Japanese control it'll be even more profitable. I wonder what the development on that side of the island would be like. Historically a lot of the Japanese investment was in or near existing Han Chinese communities, though there was violence when they started timber extraction in native-Taiwanese areas. A whole industry in the east could go many different ways: it could plant a Chinese or Chinese-Japanese colony isolating and absorbing the local communities, or it could employ those local peoples and even reduce the Sinification of the isle.
For Japan itself this would make a big difference. Taiwanese sugar basically created the gold reserves that allowed Japan to leapfrog to Power status. If jade could really be a substantial revenue stream, you'd be seeing visible differences in Japan, with a significant component being their military investments.