Re: Encoding: Referring people to a list of labels

PUA is a possibility,  although it will have impacts. The PUA in the BMP is
heavily used by Microsoft and Apple for legacy data.

If PUA is to be used for characters not in Unicode then PUA characters
would need to be excluded from all font-fallback mechanisms including the
application generic font families.

If RTL or complex rendering support  are required for PUA charactters then
graphite rather than opentype rendering would be beneficial,  and in some
cases possibly required.

Somehow I think the browser developers would prefer the status quo.