first of all I would like to send greetings from Neo...
Best solution for you will be using MultiDomain-Management. With this ou have separate management-domains, separate log servers, but you can see logs from both domains with one logviewer.
With your actual configuration you can't send logs from a gateway to a logserver in another management-domain. You need SIC beetween gateway and logserver and it's not possible to have more then one SIC-trust.
Another way to get the logs from both domains would be using a third party logserver. We had customer the are using SPLUNK. All gateways and management servers sends there logs via Log-Exporter Log Exporter - Check Point Log Export to the SPLUNK server. There is a nice CheckPoint app for splunk available, this gives you a similar view of the logs like in SmartConsole.
With Log-Exporter you can send your logs to any other Syslog-server not only splunk, maybee this is a solution for you.