So I faced the challenge of created a large custom app through the Buildfire platform. The client had a lot of custom element styles that were being overridden by the appTheme settings in the dashboard, and overriding these styles in traditional CSS fashion was growing to be a monumental task.
I wrote this small function to remove the custom styles injected into the application and so far all of the client's custom styling is showing correctly.
I figured I would share this with the community since this has been an issue without resolution for our team.
If you wish to disable the appTheme CSS in your plugin, you can simply use a meta tag in the widget's HTML, like so:
<meta name="buildfire" content="disableTheme">
This is covered the SDK wiki under the meta tag section.