(f) Training received in a multiengine airplane, a helicopter, or a powered-lift. A flight instructor may not give training required for the issuance of a certificate or rating in a multiengine airplane, a helicopter, or a powered-lift unless that flight instructor has at least 5 flight hours of pilot-in-command time in the specific make and model of multiengine airplane, helicopter, or powered-lift, as appropriate

Is this training required for the "issuance" of a certificate or rating? I think your answer lies there

Now, whether or not this is a good idea...