I think God sent Ananias to Paul as confirmation for both Paul and the church. Imagine how confused Paul must have been after such a powerful revelation! But at this point, one could still argue that it was all in his head. Though the people who were with him at the time of his encounter heard a voice, the idea of what God was saying must have taken some getting used to. After a lifetime zealously committed to a vastly different reality. But to have a vision of an 'Ananias' coming to heal you, followed by Ananias showing up to do just that would lay the matter to rest. A "verily, verily, verily" moment, so to speak.
It was also God's formal introduction of Paul to the church. Acts 9:19 tells us he spent several days with the disciples after that.
