1 Never touch multipart/encrypted and multipart/signed (but allow -I).
4 Convert dates to the current locale and timezone (with an option?)
7 Allow -d and -p accept shell-like patterns and/or regular expressions:
8 -d content-*,-content-*-encoding
11 Add option --save-as='%format' to generate names for --save-* files. Develop
12 a DSL to conditionally use values of headers, parameters and the counter.