Sorry, no dice. They will check when you arrive, even if you have a visa. According to boca.gov.tw/ct.asp?xItem=144 … e=116&mp=2 you must have proof of return ticket or onward travel.
However, there’s a way around it, depending upon your selected airline. China and EVA Airlines both allow up to six months expiry on a ticket, so you can just go ahead and book a return (or onward trip to say, H.K.) for a day not more than 60 days from your arrival, and then change it down the line. I actually got China Airlines to extend my return ticket to one year, even though I had booked it to stay in TW for 58 days. Get them on the phone and ask, ask, ask…
…or you can ask the airline about it’s change of itinerary policy, i.e. can you book the ticket that’s good for one year (remember, to set the return date for 58-59 days or less) and then call them and say you want to change the date. This is very common and most Asian carriers will not penalize you or at least have a nominal charge.
Finally, the other thing to to do is just book the one year return flight and prior to arriving at TPE, book a cheapy “visa run” type flight to Manila or Kotakinabura (both are dirt cheap right now, Kotakinabura, especially) as your proof of onward travel. Don’t show them the one year itinerary. Again, with this ticket you can change it at will and besides, I have a feeling that you’re going to either have to leave the country at least once during that year, or going to WANT to leave the country at least once during that year.
The bottom line is: show them something that says you’re leaving within 60 days and once you’re in the country, start playing the game.