Make Upfront Builder independent of Upfront theme

Hi,

Im facing a problem when running a multisite i want to let Pro sites use Upfront Builder for make a better looking theme, but for know the Upfront Builder only work if Upfront theme is activated, which is the problem.
User will have a standard website and should be a allowed to build there new theme with Upfront builder. Maybe some will use 1 day other will use 10 days, so until the theme is ready, they should be able to use standard shop theme (which dont need to be Upfront theme).

I think this would be a very useful feature for the Upfront Builder plugin.

Best regards,