I've been fighting a problem for a while now, which could easily be solved by allowing more than one field to orderby.
I want to sort my posts by X and then by Y.
eg. sort posts by X, where posts have the same X then sort them by Y.
This is a standard SQL feature, but not one currently supported by wordpress.
Currently orderby works like so:
'orderby' => 'title' or 'orderby' => 'meta_value' etc
I'd like to suggest that you allow:
'orderby' => array('title', 'meta_value')
where the order of the items in the array is the order in which they are sorted.