@kenlly this is impossible to do and this will never be in the plans.
This is the CS-Cart development paradigm - all third-party themes depend on the standard Responsive theme.
Otherwise, to put it simply, absolutely all addons, including standard ones, will stop working.
For more details, if you want, you can go deep into the documentation:
https://docs.cs-cart.com/latest/designer_guide/parent_themes.html
https://docs.cs-cart.com/latest/designer_guide/index.html