This type of feature suggestion, where a client needs to repeatedly send requests to a server to update an internal list, has been discussed many times before.
I generally try to avoid adding features that lead to heavy bandwidth usage on a server.
What you are asking is for mIRC to send a /who to all of the channels you are on, repeatedly, to retrieve the away status of every user on each channel. If you are on multiple channels, with thousands of users, that can lead to a significant load on the server. Multiply that by all of the other clients on a server that are doing this, as well as all of the other client features that do something similar, and a server could find itself under heavy strain. This would likely have the knock-on effect of the server becoming more sensitive to bandwidth-demanding requests and disconnecting users more frequently.
So, no, there are no plans to add such a feature.