Performing:

/subsystem=security:write-attribute(name=initialize-jacc, value=false)
/subsystem=elytron/policy=jacc:add(jacc-policy={})
reload

Generates:
-------------------------------------
Operation: /subsystem=elytron/policy=jacc:add(jacc-policy={})
Failure: {"WFLYCTL0080: Failed services" => {"org.wildfly.security.policy" => "java
.lang.RuntimeException: WFLYELY01024: Failed to register policy context handlers
Caused by: java.lang.RuntimeException: WFLYELY01024: Failed to register policy
context handlers
Caused by: java.lang.IllegalStateException: WFLYELY01069: Invalid javax.securit
y.jacc.PolicyConfigurationFactory loaded, expected org.wildfly.security.authz.jacc.
ElytronPolicyConfigurationFactory but received org.jboss.security.jacc.JBossPolicyC
onfigurationFactory."}}
-------------------------------------

This is WFLY part of https://issues.redhat.com/browse/WFCORE-5272. The legacy security system should set server state to restart-required.