I am looking to see if its possible first of all and then see if there is an Author willing to tackle a hopefully smallish project/addon.
I along with several others have Chat Filtered in Tabs to make it easier to read and not have all chat in one place.
I have System Chats going to another tab and since Blizz DID NOT split Guild Logon/Logoff Alerts as well as Guild Join/Leave Messages differently than System Alerts, I miss them all.
I would like to have an Addon Filter those Specific Messages either back into a certain chat tab OR (if easier) have them appear in the Blizz Error Frame / MSBT Frames OR both! 
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I would be forever grateful and happy!