Hi Sascha,
I had a look at the plugin and i found at least one missing action:
I miss 'update' user and domain details. this should be possible. 
what about a "get_user (single and all of the reseller)" and a "get user and domain details from a specific user" action ?
this would be a nice improvement and would help to develope applications that could interact with the api from another server or Windows.
I hope you know what i mean.
greetz
FISA4