Prevent Sass framework variable collisions - import

Question

Is there a way that I could import multiple framework Sass files in a way that each framework will use its own variables without the variables of one framework overriding/colliding with the variables of the other while I would still be able to access the variables of one or both of those frameworks in subsequent styles as needed?
For example:
framework-a-variables.scss:
$border-color: green !default;
framework-a-box.scss:
.box-a { border: 1px solid $border-color; }
framework-b-variables.scss:
$border-color: red !default;
framework-b-box.scss:
.box-b { border: 1px solid $border-color; }
app-styles.scss:
#import 'framework-a-variables';
#import 'framework-a-box';
#import 'framework-b-variables';
#import 'framework-b-box';
This will result in an element with a box-b class having a green border due to how Sass variable declarations and the !default keyword work. Likewise, if I wanted to use $border-color as defined by framework-b-variables.scss in, say, button-styles.scss, I wouldn't be able to.
I have tried using placeholder selectors to scope the Sass imports so that the variables initialized by each framework are scoped to be used only by the other imported files of that framework. This seems to scope the variables as desired, but none of the styles are compiled unless I extend the placeholder selector, but Sass requires that extend directives be used only within rules and I wouldn't want to increase the specificity of all my selectors just to achieve this.
%framework-a-scope {
#import 'framework-a-variables';
#import 'framework-a-box';
}
%framework-b-scope {
#import 'framework-b-variables';
#import 'framework-b-box';
}
#extend %framework-a-scope; // This is not allowed in Sass
#extend %framework-a-scope; // This is not allowed in Sass
html {
#extend %framework-a-scope; // Wouldn't want do this
#extend %framework-b-scope; // Wouldn't want do this
}
I have also tried using mixins to scope the Sass imports. I believe that mixins, unlike extends, can output rules without being nested within rules, but Sass does not allow import directives within control directives or mixins.
#mixin framework-a-scope() {
#import 'framework-a-variables'; // This is not allowed in Sass
#import 'framework-a-box'; // This is not allowed in Sass
}
#include framework-a-scope();
So, is there any way to achieve what I am looking to achieve? I don't mind having to explicitly import variables in specific scopes when needed, for example:
.my-custom-box-1 {
#import 'framework-a-variables';
border: 1px solid $border-color;
}
.my-custom-box-2 {
#import 'framework-b-variables';
border: 1px solid $border-color;
}