I believe GeoServer requires that filters passed in a WFS POST request are in the OGC XML based format.
If you make a GetFeature request to GeoServer using a GET request the filter can be CQL or ECQL and GeoServer will accept it.
Will GeoServer ever be able to accept CQL in a POST filter parameter or provide an endpoint which will convert it on the fly into the XML based filter?
Alternatively, do any of the other web servers handle this better?
Currently our layers are filtered using CQL for the WMS requests so it would be great if the WFS GetFeature requests were using the same filter format.