I lean toward the first suggestion. Although Keith's second option is
more flexible, I think it will delay widespread adoption of
Content-Disposition.
If it were just a technical matter, the second one is clearly superior
(defers character set switching issues, allows the possibility of
transporting things like ACLs as part of the disposition) but it makes
the whole MIME package and cdisp in particular a lot more byzantine.
I'd hate to see each MIME extension have its own parameter encoding
scheme. If we can come up with a scheme for doing binary transparent
fields that can be used for all future MIME extensions (e.g.
Content-Disposition, PEM, maybe DSNs, and who knows what), it would
make MIME as a whole less byzantine than otherwise.
Keith
p.s. I say "maybe" DSNs because some DSN fields also need to work as
ESMTP parameters, which makes things more difficult.