Client IP for use with mod_remoteip and X-Forwarded-For

[sbmechanics]

When using X-Forwarded-For, GelfHeader and GelfFields (X) works well except when using mod_remoteip (for allow / deny / etc.). When RemoteIPHeader X-Forwarded-For is used with RemoteIPProxiesHeader, mod_remoteip removes the X-Forwarded-For header and records it to %a (Client IP address of the request). As X-Forwarded-For is no longer in the header, it cannot be picked up using the GelfHeader method.
Could a GelfField be created for client IP address / %a?