Commentators are difficult.
Even on a heavily funded game like Madden, in which actual NFL Commentators do the voice over from actual scripts, it sucks.
I mean, it's cool and all... but then they go off on some tangent that had nothing to do with the play. All the time. Highly inaccurate.
I've played games with Text Base Commentators, and it pulled from Play Logic and stuff, so you could get "RB McCarthy bounces the Sweep outside for 7 before being pulled down by FS Jonah". But we basically get that in the Play by Play. They just add more 'color' in the Broad Cast version, maybe adding it the Play Type or if it was a Blitz or not.
The key is accuracy. You'll get a Sack on Madden with your DT while in Quarters 3 Deep Man, and then they start talking about how effective your Blitzing is, despite the Game knowing what play you picked and that it wasn't a Blitz. Would be WAY more awesome if it recognized, and talked about 'When a Front 3 can get pressure like that, you CAN drop 8 into coverage.'
But then you are really talking about a system where the Game extrapolates Game Data and generates Accurate Text about it... so it can be clunky and difficult.
Either way, it would be awesome if accurate. Best of luck working on it!