I would use a system template per FGT model. If you have to mange many different models, yes, you have to create many different templates since it's referring the physical interface name. But likelihood is you need to manage some other device config as well with those templates if you have many different models to manage. And those are different per model and need to have different templates.
same here but still administrative services are device config and cannot be configured on a normalized interface. Normalized interfaces are just a reference to be used in a policy that tells FMG what interface to use when the policy is deployed to a Fortigate...
Interfaceconfig (ip, adminservices etc) has to be done in Device Manager per FGT or - if that is possible - maybe via provisioning template.
"It is a mistake to think you can solve any major problems just with potatoes." - Douglas Adams
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.