From page 267 of Richard Davidson’s important study Typology in Scripture:
The apostle is not dealing with abstract ideas or meta-historical descriptions. The force of Paul’s whole argument rests on the historicality [sic] of the events under consideration. For Paul it is essential that the events really happened. Only thus can he draw out the significance from Israel’s real history for the concrete experience of his readers. If the events of salvation/retribution did not for Paul actually occur, he would not have been able to utilize Israel’s experience as a devoir-etre argument in his paraenetic warning to the Corinthians. We therefore cannot underscore too heavily that for Paul the historical nature of the event is an integral element in the structure of the τúποι.
This quote comes from an extensive exegetical discussion of 1 Cor. 10:1-13, in which Paul not only makes a typological argument, but describes something of how typology works more broadly. For this reason, Davidson uses this passage as a typological control. If Davidson is correct in his exegesis, and in his understanding of the importance of the passage (which I think he is), then any rejection of a historical Adam would seem to founder on the rock of typology. If historicity is a typological necessity, then Paul’s use of Adam in typological arguments means that Paul believes Adam to be historical. So on one side of the debate, you have the Apostle Paul. On the other side of the debate…Did I mention that the first side has the Apostle Paul? I think we’re done here.