More flexible knowledge base design and layout, including custom HTML/CSS

Writing on behalf of a customer here, it seems like there is a need for more customisability options for the browser page as well as the mobile page.
Currently, the mobile footer on their mobile KB page as the links are stacking up unevenly.
Additionally, it seems like we are not able to customise the font of the breadcrumbs on the KB as well.
CSS styling capabilities is needed here!