There is, of course, no need for more Apostles to testify to having seen the risen Christ ... that FACT was established by 2 or 3 witnesses already.
There is also no need for Apostles to write down Holy Scripture, since that task was also completed.
In that regard, the Church (Body of Christ) does not NEED another Paul to add to scripture. (I agree with you.)
However, nothing in scripture prohibits Jesus from appearing to someone as He appeared to Saul ... so God COULD create an Apostle and charge that Apostle (one who is sent with authority) with a mission. The Holy Spirit could certainly also raise up individuals and command them to "go" and "do" whatever task God might appoint them to ... which would make them no less an 'apostle' than Barnabas or Timothy (who were both "one sent").