Apache Solr Custom Sort

Solr Custom Sort is a module that I made for the Air Miles Project. By default, Apache Solr doesn't allow you to add sort types. Basically, you can only use those that are standard set in advance. For the Air Miles project, this wasn't what we needed. Therefore, I'm now working on the Custom Sort module, a module that allows me to add multiple sort criteria, with the ability to manage them all.
The challenge for me is now to get transparency. Today the module can only be managed by administers but in the future this should be possible for all users.
The solution was simple, we just had to overwrite the class that is implemented by Apache Solr.

variable_set('apachesolr_query_class', array('solr_custom_sort', 'Solr_Custom_Query'));


Update : The module is finished and ready for download. More info here.