The use of progressively sized notes have been used in many counrty for iliteracy and the sight impared. Also, the same has been done using overall color to designate denomination.

Braile has been used on coinage but first made its debut with the new Canadian currency. Bumps can be felt on the corner of the note distinguishing the denominations.

Large dots and bars have been used for the sight impaired (but not completely blind) for denomination recognition.

The numbers are larger on the (newer) US currency for the same reason.

(opinion)
I think braile is a wonderful idea, but as the note wears the bumps become less distinguishable, the same could be done with small holes (holes don't wear out- so I'm told).