Template ResponsiveGrid should accept only componentA. componentA has its own ResponsiveGrid

Requirement:

Template ResponsiveGrid should accept only componentA. componentA has its own ResponsiveGrid, that should accept other components. We can have any number of componentA and componentA can be added dynamically on the created page.

For Editable Template, We have Policy configured to accept only componentA for Template ResponsiveGrid. Default, 1 componentA is configured on template (after a page is created using this template any number of componentA can be added dynamically). When we try to configure Policy on ResponsiveGrid of componentA on template, it is only applied to default componentA.

How to apply policy at component level?

Can we apply policy at component level?

Is there any ootb way to implement our requirement?