The idea is that templates could be referenced/nested. For example, you would create multiple templates using barriers and kerbs. However, instead of the barriers and kerbs being "live" in each template they would be referenced in from another template. This would mean if I have used a barrier in ten different templates and I needed to update it, I would change it in the source location and it would update in the ten locations it has been referenced into. This would make templates much easier to manage as you would just need one instance of a template component (barrier, kerb etc). This would benefit all users as it would save time and increase quality.
Oh, Gawd yes!
I have already seen where the client specified one combined curb & gutter, then came back for the next design phase with another combined curb and gutter.
I understand that I could define all of my template components with parametric values, but it would be easier to have the option mentioned above - fewer variable names to keep track of. That way I could make the adjustments to my "subassembly" and it would perpetuate through my project, instead of having to go into every template that uses curb and gutter to manually edit each one (and always missing something on one or another).