Consider this verse:
Acts 6:2 Then the twelve called the multitude of the disciples unto them, and said, It is not reason that we should leave the word of God, and serve tables.
Who is included in this group of twelve? Paul wasn’t saved yet, so he’s not the twelfth. Judas is dead, so the writer of Acts (Luke) also acknowledges that there is a “twelfth” apostle. I believe this is another testimony that the decision to choose a replacement for Judas was the right one.
I have never doubted that Mathias was “counted” as one of the new twelve. I just believe that Peter was in error in doing what he did. That’s all. God had Paul in mind if there were going to be any replacement.
That brings out another question. If Apostolic Succession was to be infered because of Peter’s actions... where are the OTHER eleven apostles now? Assuming, of course, that the Pope is the apostle of this era. Shouldn’t there be twelve at ALL TIMES? In other words, Apostolic Succession never happened after Acts 1, did it?