Happy to consider such a feature but I'd want to be able to reproduce the problem and be able to verify that this actually resolved a problem, as I'm skeptical that the traditional 2nd level cache could be the primary bottleneck of such an application.

Hibernate ORM introduced recently a feature to use the 2nd level cache via "reference caching"; I wonder if we could use that. For example it would be expected if the ORM caching configuration enabled reference caching, that the Search lookupMethod set to SECOND_LEVEL_CACHE would automatically use that feature too.