I'm not keen on adding a checksum field to the Content-Transfer-Encoding
header. Clearly only the base64 can profit from having a checksum
available.
This is far from clear. quoted-printable and binary definitely can benefit
from checksums. For example, I can, and do, create quoted-printable objects
that are totally resistant to BITNET munging even a single byte of them.
binary is an even better example, of course.
As such, I think the way to proceed is simple:
I disgree with your approach, given that your initial assertion is, in my
opinion, false.
Ned