This module makes it possible to assign each toplevel product family its own theme.
You can make Shop-in-Shop effects based on Brand, target groups and product types. Each theme has its own color scheme, logo and layouts, so you can achieve a "department store" look, where different departments have their own character.
Less comprehensive but at least as effective, is the option to copy your theme and then customize individual pages like product pages. This allows some groups to appear with comprehensive information while others will have more simple layouts like spare parts.
You choose your main theme, as usual, and then change the theme for one or more of the other categories at the top level.