It actually looks like no one here can, or wants to, think outside the box. While I doubt that most classic Amiga models could cope with this, Even I have an 040 fired A2000 - no USB yet, but that apparently easy to fix....
Better buy a USB board while it's still available. Stocks are running lower and there won't be another production run of the Deneb.
About the Kinect, for me, it is the NextBigThing(TM), just look at the various YouTube videos. As for the use on Amiga: Only the Deneb would be able to drive it. Stuff like this needs realtime Iso transfer support, and no other HCI driver on Classic/Morphos/Aros/Aos4 is able to provide this.
But even if you would be able to port the open source driver, and though a 68060 might just be fast enough to capture the two video streams in realtime, it is very much impossible to process the image data in time to obtain useful information from it.
Sorry, this seems to be a pointless effort to me.