If your appliance only needs to facilitate communication through the Cloud Service Appliance (CSA), then you only need to make sure that ports 80 and 443 are open for internet traffic to get through the CSA to the Core. If by making these changes you are anticipating that the clients will be able to talk to the core directly, this list appears complete but make sure to double check it against Ports used by LANDesk Management Suite - Full List.
If you need clarification on any of the points please let us know.
Can you say what functionality we would lose by not being able to enable ICMP pings? Since it doesn't have an associated port, there is no way to add an exception to the Meraki for pings.