That's fair and what you say makes sense in that context. Crockford doesn't have U/V problem either by the way, because it doesn't have U in its alphabet. It's

That's fair and what you say makes sense in that context. Crockford doesn't have U/V problem either by the way, because it doesn't have U in its alphabet. It's only missing aliasing for it, so there is no possibility of passing on the wrong value by confusing V with U. That just leaves 5 and S. Whole another standard just for that might be acceptable if the use case you mentioned (mostly upper-case) gets significantly more benefit from it.