Subsite with different template, and content

The framework is not the problem. You just need to exclude your Consulting category from the loop each time you have it. Then use a custom template for the marketing page. Another option would be to set up a multi-site install and then use Consulting as its own blog.

EDIT:

To exclude the category try adding this to your themes function.php

function exclude_category( $query ) {
    if ( !$query->is_category('consulting')) {
        $query->set( 'cat', '-1' );
    }
}
add_action( 'pre_get_posts', 'exclude_category' );

Edit 2: fixing the problem chip mentioned below.