So you publish your Management Server on a Public IP through the Local Firewall.
You will need to allow the Check Point Services through from Any Source as won't "know" the DAIP IP is
Define the Gateway as normal but set as a DAIP
Deploy the Gateway physically and determine the actual IP on the External Interface that has been picked up
Establish SIC on the Object and will ask you for the IP currently in use
SIC establishes and will be able to complete the rest of the way.
As managed by the same Management then the Certifcates will be known and authenticate with the Certificates.