Just some design concepts for getting up wind... with out the need of a rudder- but a deep keel!
Depending on the size kite / wind strength the mounting & rings might have to take quite load.
There is an alternative to useing a ring of less than 360º but that would require the "tack" to turn the whole vessel around! The idea is a major addition/complication as it would need a clear run all the way around the vessel and nothing can run over the top of it. - Although the double ring would also work as a safety banister if mounted waist high- "killing 2 birds with one stone".
the Tacking process.
[caption id="attachment_1346" align="alignnone" width="450" caption="Tacking process. (wind from the North, vessel heading from south to north / bottom to top)"][/caption]
A concept for the runner...
[caption id="attachment_1350" align="alignnone" width="450" caption="Kite runner"][/caption]
Material wise- the rings could be made in the same manner / same material as windsurfing masts, but you have the added problem of the point loading of the wheels - instead of runner wheels on the inner side a "sled" could be made to distribute the force on the rings.