I believe that since he has a job that is online, he is able to work anywhere in the world. He should only be concerned of his legal status in Canada as a visitor. If he can only stay for 6 months or so in Canada, than he should apply for an visitor extension, so that he can legally stay longer in the country until his PR is done. Keep in mind that he still may receive mail in Taiwan to meet up for an interview with the CIC, regarding his PR, if needed. So yeah those are the 2 things he'd have to worry about: how long can he stay in Canada, and how will he get his mail.
He still has to have strong ties in his home country, but that shouldn't be too hard to prove. The fact that he has a job, and is able to continually provide for himself while visiting you in Canada, without having to rely on limited savings, is the ideal visitor. As far as im concerned he shouldn't have a problem staying with you and also working online, as yal wait this out.