It's quite useful to be able to perform multiple code translations (and multiple validation steps) as part of a single call. The simplest level of this would be to use a single ValueSet or ConceptMap and multiple codes/Codings/CodeableConcepts. Ideally, you'd be able to pass in multiple pairs. E.g. "Validate Coding 1 against ValueSet 1; Coding 2 against ValueSet 2; etc.". For performance reasons, it may be adventageous to validate all of those with a single call rather than a whole bunch of separate calls.