We'll certainly look into it. Just please understand that RFCs are guidelines and not technical specifications or requirements and that some RFC implementation can prevent implementation of other features and may require additional changes. While I doubt that's the case in this situation, I just wanted to mention it. 

I am adding this proposal to our future feature request list for further consideration and possible implementation.

After further review with the dev. team, we will be implementing this request in the next minor update.

We have added the version to the XMPP stream.  It will be included in the next SmarterMail 13 minor update.  Additionally, XMPP now uses SASL authenication and has TLS capability.