Actually the Ideas is:

Example:
We can able to create 3 different layout templates for Blog CMS:
Assign the Template 1 to Blog 1
Assign the Template 2 to Blog 2
Assign the Template 3 to Blog 3


When we visit the all 3 blog pages we will see the designs as per assigned templates.

We should able to assign the templates via CMS Field.

Sometimes clients have different content for CMS Items and we should able to create the design accordingly to make them happy.

Suggestions are welcome!

Thanks.