Enterprise databases are filled with users usurping a field with pre/post-pending characters to mean something special to them. Even filenames have this problem due to limitations in directory trees. Inband signals will never go away.
At some level everything has to go in a single band. I don't have separate network connections to my house, I don't send separate TCP SYN packets for each "band". I don't have separate storage devices for each file on my harddrive. We multiplex the data somewhere. Yhe trick to it is that the multiplexer has to be a component, and not a distributed set of ad-hoc regexes.
Strictly speaking, that only works with a three second delay between the third + (at which you receive “OK”, indicating a mode switch from data mode back to command mode) and the AT command (which is then interpreted as a command and not data).
Anything that would hang up on seeing that string as a monolith was operating out of Hayes spec.
