Pros: Uses simple policy constructs. OPA will index the allow rules and yield constant-time eval. See https://blog.openpolicyagent.org/optimizing-opa-rule-indexing-59f03f17caf3
Cons: Maintaining policy manually could be painful. This could be solved by rendering/generating the policy.
# Allow group "techlead" to do anything on subscription "X".
allow {
input.subject.group = "techlead"