I'm very much interested on standarize as a XEP the actual message exchange scheme that occurs between the asterisk-im plugin and the asterisk-im handler on the client.
In fact, it is not related to Asterisk, but to any external phone system. It allows to operate on the phone system at the same time that tied the presence awaress to the phone operation status.
Why? We've implemented a Cisco CallManager-IM plugin based on the same message scheme used by the Asterisk-IM plugin. Well, besides to be able to call and forward calls, it can hangup, redirect calls, put and remove forwards, hold, unhold, login and logout from the phone, capture calls, conference, etc.
There are still other operations that are interesting to implement like park/unpark calls and other call center related functionalities.
However, without an XEP related to handling an external phone system is hard to build interoperability between clients and server-plugins.
If there is anyone interested in these issue? If none answers, we may go and present our own proposal for a XEP in this topic.