there's this issue open since some time: https://issues.jboss.org/browse/ISPN-31
but it doesn't look like it would fit what you're looking for.
When using Hibernate with Infinispan as a second level cache this is usually configured with cluster mode "invalidation", but you could certainly configure it instead as "distribution" or "replication", that would give you some degree of availability for a limited set of read-only operations. Writing transactions would still need to connect to the database with such a configuration, and that's where OGM becomes interesting.
the problem with implementing an Infinispan CacheLoader is that it stores data in a "map" API, so you would receive keys and values. I guess one could implement a trivial JPA based cache loader which stores everything in a simple table having a key and a value column (and that's what is about ISPN-31 as far as I understood), so the only difficulty would be to implement the value with a large enough @Blob.
I guess what you really want is to store the values in a structured form? I'd try OGM in that case, and have it persist via a JdbcStringBasedCacheStore in a database for non-volatile storage. Keep in mind OGM is currently in development and while the CRUD operations are fine there are some limitations on which queries it can support.
To guarantee Height Availability the application needs to run an multiple nodes. Therefore all data has to be put into a distributed cache like Infinispan.
did you consider the "standard" alternatives, like using a relational database in a failover configuration?