DRM : 7 bit ASCII teletype 'subchannel' : possible elemination of numbers
stations as an end product!

One forgets that DRM technology is improving all the time.
In 3 or 4 years a very portable DRM reciver, with a menu system could be
reprogrammed via a smart card.
A smart card or memory card (possibly with with a keypad and display) has
all the crypto power one needs.

-=-=-=-=
Barring that, a USB connector to a modified MP3 player would work just as
well.
You only need a file system that has 2 partitions, one for permanant system
files -- the other for files that can expire!
Modern computer file systems don't support 'file expirey dates' -- but self
expiring file systems can be designed.
A modified Win-NT file system would do, or even better yet -- modify a LINUX
file system.

=-= Message =-=-=
DRM -- if it had a 7 bit ASCII teletype 'subchannel' type added to it,
could
eliminate numbers stations...

Binary files can be transmitted using only 7 bit ASCII chars, preferably
with a little error correction.

Except for the fact that you have to lug around a laptop computer... which
could easily be stolen or confiscated by the security forces of whatever
country you are in and checked for programs such as the one you mentioned,
let alone the decoded text. All of which would easily compromise the
agent.