Hey Tommyb,
Bindings can be fun but the weight is an issue, adds heaps to the board making some tricks more difficult. A good thing to look for in bindings would be ease of getting into and out of. The boots that lever lock open or ratchet open are great for getting on and off quickly whilst flying the kite in the shallows. When flying a kite you want to be able to put your boots on easily with one hand.
LF Deep suctions used to be the go a couple of years ago but then you always need a bottle of dishwashing detergent to get your feet in. I rode with Nice 13's which had a ratchet system and a hinged front section making it really easy to get them on and I could ratchet them down til I cut off blood supply if necessary.
Comfort is another critical factor, nice soft cushy foot beads are important and this may be different to wakeboard bindings which you might wear for 5 to 15 minutes at a time whereas kiteboarding bindings go on and can stay on for hours at a time.
Most if not all wakeboard bindings will fit on a kiteboard as long as the kiteboard was made to take bindings ie the Airush 136/146 Wake or the new Airush T3 for example. They come without pads and have inserts ready for bindings.
Saffer is right, Wakeboards can and have been used in kiteboarding for ages but with their increased rocker they suck at going upwind compared to a dedicated kite board. Still good for doing epic downwinders where you have waves to jump off and no need for going upwind.
It's all part of the sport, there are no rules! If it floats your boat, then do it. Comfort and ease of getting in and out of is key and just have fun. Probably best to buy 2nd hand where you can try em on first. New bindings are outrageously expensive!
Good winds,