Perhaps a wholesale replacement of 'character set' by 'charset' might
not fly (if only because the replacement terminology hasn't been
agreed on), but at least some introductory remarks about the informal
notion of the phrase 'character set' in these documents might help.
I do not think it is wise to be in direct conflict with ISO
teminology on this issue. To use the term "character set" for
what ISO calls "coded character set" , and ISO having another term
"character set" menaing something else, is not a convenient
situation.
Within the Internet, the terminology used by ISO is largely
irrelevant. Using ISO terminology might aid those who are already
familiar with ISO protocols, but it will only confuse the majority of
readers of the MIME RFCs.
I'll also note that the MIME term "character set" is NOT the same
thing as the ISO term "coded character set".
Keith