My understanding,
If you don't have the type rating before coming to CAL, you will have a type rating based on a Taiwanese licence.
Your country CAA may or may not accept, the equivalence afterwards and quite a lot WILL refuse because Taiwan is not ICAO approved (due to the special political situation). So in fact, it may be impossible for you to put that type rating in your primary licence without a lot of sim/ground checks...
If you have the type rating before coming to CAL, the easiest (and cheapest...) is to keep your other licence valid by passing the medical.
JAA, for ie, accept to put on type rating with the mention "restricted to China Airlines", if you prove you succeeded reccurent checks in CAL and have the hours. To get, a "full" JAA afterwards, you only need a Prof-check with a JAA approved examiner.
Now, if I am wrong, just flamed me.
The best solution, IMHO, is to ask your CAA beforehand what will be their attitude regarding a type rating on a Taiwanese licence.