Getting the messages out of SE chat won't be the difficult part, that's been done before and it's dead easy
Getting the messages into TF2 might be slightly harder, given that it's ancient, has no real API, and requires you to interface with Steam which may or may not require two-factor.
I'm... only too familiar with it. Developed a bot framework based on it which at last count was being used in about 10 bots around the network; SmokeDetector runs on it; I've contributed directly to it
@ArtOfCode Out of curiosity, how were you displaying the messages at the center of the screen earlier? I don't know of way to do that with vanilla console commands (not counting tv_msg or spawning a game_text)