True, and definitely an argument to consider full numeric. I am sure they've thought about that already and decided against though, so I didn't want to go that far.

Also, in practice today there are not many people anywhere in the world who are not at least somewhat familiar with the Latin alphabet to the point they wouldn't be able to recognize/read/write the letters, and (possibly excepting a few old typewriters here and there) people would generally be able to enter letters of standard Latin alphabet into whatever devices they are dealing with.