Ofcourse, it should be a option, not the default.As an option it would be nice. The default name/value pairs should not be changed, as it could break a lot of 3rd party software.
Just an idea, on which I've not though much yet... isn't it possible to write a plugin, which would transform answers from directadmin to XML format? I mean if it's possible to set a proxy script somewhere, which would re-send requests to Directadmin and transform replies to the format you need... I could probably write it, or at least consider the possibility of writing it, if there would be enough requests.