The answer is: you would NOT, there is no way to make rulebase changes on a Check Point firewall without the management server.
(unless you are a Check Point developer maybe
😉 )
You need to make sure you have a good backup of your environment, either created a daily migrate export and move it to another box or run a complete GAIA backup, which will include log files.
With a good backup and the availability of a VMware server where you can spin up a new server, you should be able to get back into business within 2 hours with either an import or a restore.
Regards, Maarten