Add more discussion.

pep-0383.txt

@@ -104,7 +104,10 @@ has the limitation that chosen representation only "works" if the data
 get converted back to bytes with the python-escape error handler
 also. Encoding the data with the locale's encoding and the (default)
 strict error handler will raise an exception, encoding them with UTF-8
-will produce non-sensical data. 
+will produce non-sensical data.
+
+Data obtained from other sources may conflict with data produced
+by this PEP. Dealing with such conflicts is out of scope of the PEP.
 
 For most applications, we assume that they eventually pass data
 received from a system interface back into the same system
@@ -134,6 +137,11 @@ from which the encoder would create the desired bytes.  In fact, with
 python-escape, there are required byte sequences which cannot be
 generated from replacement Unicode.
 
+A few alternative approaches have been proposed:
+
+* create a new string subclass that supports embedded bytes
+* use different escape schemes, such as escaping with a NUL
+  character, or mapping to infrequent characters.
 
 References
 ==========