There’s a good FAQ about the Working Holiday visa here: https://www.youthtaiwan.net/WorkingHolidayen/cp.aspx?n=88E18DB22818E550&s=8133A77AC99AE860
It states fairly plainly that despite offering a work permit the main purpose of coming to Taiwan has to be holiday-related. Therefore, for example - if the aim was to come and work full time for a year, appears to be against the conditions of the visa, regardless of industry.
If it was more of a part time/supplement cash on a holiday kind of deal, it depends on the country of the applicant as to how long you can work for a single employer or the qualifications. For most countries, there is a limit to the amount of time you can work for one employer - usually 3 or 6 months. The entries on the regulations for some countries mention the need for qualifications to be recognised, but doesn’t mention which types of industry that applies to.
Hope some of those links help nail it down for you.