I think for futurization with other ciphers and with other applications using these ciphers, it may be necessary to support either binvar content or hexadecimal strings.

My argument would be to automatically detect and support a &binvar if that &binvar presently exists, else treat it as a literal string that happens to begin with an ampersand.

Well. At least I won lunch.
Good philosophy, see good in bad, I like!