XML-RPC API wp.getPosts custom filter

I have successfully created a script for accessing WP content via the XML-RPC API. While doing tests, I noticed I am limited to specific fields which can be filtered. I am curious to know if there is another way to do something like this:

$filter = array(
     'sticky' => true,
     'post_type' => 'post',
     'post_status' => 'publish'
);
$MyClass->query('wp.getPosts', $filter);

Currently, the XML-RPC server is ignoring all filter keys that are not the ones specifically mentioned in the API’s documentation. Is there any around this without having to created a plugin to extend the API?