Ok, now, last I remember, EUD conditions were still valid, weren't they? Ideally, that's all you need to perform actions based on text...
SF with a special patch could handle EUDs back in the day... I think I still have it... but now, how to look up the values that need to be tested for this to work...? Anyone who knows how those mem adresses and whatnot work upto the challenge?
I was actually looking for the exact same system, just for a slightly different purpose...
Actually, on that note, couldn't this potentially desync the game? depending on the message, which could be sent to allies, specific players, or even whispered, not all players would see the same text on their screen... wouldnt that crash everyone who doesnt see the text? (as on their system, the condition isnt fullfilled, etc, etc...)
EDIT: Looking through some of the stuff here, looks like this was already looked into... now, to delve in to make this work