Please do not confuse being licensed (with an type rating on a licence) with a Company OM Requirement. One is legal, and one is what the company does.
Provided the individual has the rating, then you can Line Train them with an OML. HOWEVER, your OM-D may have requirements above the basics, so you'd be best to review in there.
LTC is a Company Appointment after all.
I've never come across an insurance requirement for a final Line Check. Common sense also says how would you be able to Line Train???? Every insurance policy i've purchased is defined in terms of minimum licence required and stipulated minimum hours of experience.
You will not find a clear definition of CRMT as it is now. However you can see you instructional limitations within Part-FCL.