Well I went to the Bureau of Consular Affairs yesterday, and they told me that you don't need to go to your home country, but you have to leave Taiwan and apply for a student resident visa at a Taiwan Overseas Mission
Here are the documents you need:
1). Completed Application form (available here:
https://visawebapp.boca.gov.tw) and six photos
2). Passport with at least 6 months of remaining validity and two blank pages (original and copy)
3). Admission letter from your school
4). Health certificate (you can get it done at the same places as your work ARC health checks)
5). Bachelor's degree diploma (original and copy authenticated by Taiwan overseas Mission and transcript authenticated by Taiwan overseas mission. She said one is okay, but I'm going to bring two)
6). Financial statement showing that you have access to more than 500,000ntd.
7). Other documents may be required on a case by case basis
It's gonna be a lot of work assembling all those documents! Good thing school doesn't start until the Fall!