If 18 is not in your definition of "older" international amateur pitchers, you've completely limited the sample of high profile arms. The only two I can think of in recent years who signed at 20 or older are Paniagua and Rafael DePaula (Yankees). I would never want to intentionally limit the talent pool. Like you, I have no problem passing on high profile 16-year old Latin American pitchers. I'm ok with never signing any high-profile IFA arms.