Yes bunji necklace should also do the job for the knife function, are they all in Stainless steel?
Almost right, but you have to be a little careful and have one bar per kite, often more than 500$ now... I have only 2 bars (23 & 27m) in plug and play mode for 3 kites (6/9/12) depending on program (wave, freeride, freestyle) and conditions, covering a very large range in seconds.
Also depending of the spot. In clean sandy beach, you may be as quick but if there are some obstacles on the beach that make your lines turning on themselves not well, I'm pretty sure the kitecleat will be quicker, from a little to a lot in some "half spots" that I know.
You are welcome for the idea!
Not sure it will last very long because of corrosion.
Anyway, an independent review of prototypes there: http://www.wetestkites.com/tag/kite-cleat/
Since then almost 1500 kitecleat sold, so thanks a lot to my users, welcome for others and yes, it's not absolutely necessary to have one to practice kiteboard!