question about valid chars for charset names

[Markus Scherer <markus.scherer@jtcsv.com>]

Another question:

Mark quoted the charset name ABNF including

mime-charset-chars = ALPHA / DIGIT /
"!" / "#" / "$" / "%" / "&" /
"'" / "+" / "-" / "^" / "_" /
"`" / "{" / "}" / "~"

This seems overly broad for any kind of identifier, and I know that the current list does not include characters like '{', '}', '#'.
It also looks like any of these can start a charset name, not just ALPHA/DIGIT.

Why is the set of valid characters for charset names so broad, including all kinds of punctuation?
Is there a chance to restrict this set in the future, removing punctuation that is not currently used?

markus