You don’t need to worry about the JMM while using Multiverse. The JMM is defined in happens before rules, and Multiverse provides a happens before relation on a transaction commit and transaction start. It probably will be based on a CAS write and read of object state. A CAS write/read can be compared to a volatile write/read and the last one is one of the before rules. So one of the things you can say goodbye to is using volatile variables.
Multiverse and the JMM