Easier solution would be not to chat with people who insist on keeping their away status enabled when they are not away.
Getting into technicalities: it shouldn't be mIRC's "job" to bend around people who insist on using IRC the wrong way.
Away status together with away message exists for a reason and that is to inform you that the person you are messaging is away and thus cannot answer you. If that person in fact is not away they should cancel their away status.
In fact mIRC has even that angle covered with optional setting "Cancel away on activity".
So from that perspective I really see no reason why mIRC should have feature like that implemented. For the select few who are in a situation where they need to regularly chat with people who insist on keeping their away status enabled while they are not away the simple solution would be to use the script you provided in your post.
