I've cobbled up a sort of "addon" package. This only adds handling to the VNC console, for the SparkGateway only (I don't have time just yet to spend adapting the RDP's SWF section. The java applet was much simpler).

Anyways, this requires an added line in config.php like so:
/ Use SparkGateway for RDP. Enter the gateway's wss:// URL here (without wss:// ) /
var $consoleSparkGateway = "tsaukpaetra.com/services/SparkGateway";

The zip file should be unzipped from the root of the phpvirtualbox installation. It should replace only one file.
The zip contents contains the basic files needed to connect to the sparkgateway directly (without user input) in the form of vncdirect.html and rdpdirect.html.