I don't see why you would preach through a Catechism. I think that's something you should teach your church in Sunday School's or Small Groups to get them sound in doctrine. As far as preaching on it? I personally think Pastors should preach through a book rather then preaching through a Catechism.
Don't get me wrong. I understand the Catechism is based on the Word of God, and it teaches it. That is all the Pastor would be trying to do. I suppose it would be a beneficial thing to do.
For example: The church I'm currently joining, their Pastor has been preaching on topics he thought the church needed to hear about due to certain issues. For the 6 years before that he preached through books. So I can understand doing things like this if the Pastor feels it's needed. I wouldn't make a practice of doing things like this though.