BWJM and JB105, I think you're right.
For example, if there ever was to be a $5 AOQ note, people would get them mixed up with AOO (if there is to be an AOO released).
However, I believe that there are no AWQ or EWQ $20 notes released because people would get the prefixes mixed up with AWO and EWO, since the letter "O" looks like a number zero, and the letter "Q" looks more like the letter "O". I really think that the BoC should keep the series letter "O" as a third letter.
By the way, is there any way of knowing if there will be a prefix AOO on a future Journey $5?
Later, Jonathan