Technically the firefox profile can be hosted anywhere. It is just inserted as compressed encoded to base64 string in the invoking script.

You can create a packed firefox profile which includes any installed Firefox plugins:

cd /your/profile
zip -r profile *
base64 profile.zip profile.zip.b64

Usage example:
$web_driver = new WebDriver( $wd_host );

$desired_caps = array( "firefox_profile" => file_get_contents("/your/profile/profile.zip.b64") );

$session = $web_driver->session('firefox', $desired_caps );