From what PagerDuty has said, we may be able to alter how the alerts are sent to PagerDuty from Meraki, but we would need to change the Javascript that the hook is written in. No one here has enough JS experience to want to try that, and we have better things to do than altering that code.
Actually I have already written an HTTP server/event parser as an interface between N-Able/N-Central and PagerDuty. But, because we don't have the certificate for SSL on the server that runs it, I can't get the Meraki webhook to talk to it.