Water injection is neat stuff... but I've come to enjoy reliability more than neat lately. I've made well over 300 on stock zx10 motors with pump gas and water injection... but they are time bombs... water injection is just not reliable in it's current off the shelf technology. I hate saying that, but that's been my experience in about half a dozen builds at this point, and more than one high performance tuner has shared with me the same. The right fuel just plain works, all the time, and is a shit ton less likely to go wrong.
ZX12's were tough little bastards, and that extra displacement goes a long way. That era of big bore motors from the Kawi/Suzuki were just crazy with their power potential & strength. Doing the same on a modern 10R motor takes a lot of good thought, or a whole lot of luck. I've never been the lucky type, though. Something about all the lightweight architecture and insanely high revs make them a little more difficult to push to 3 times their normal output (and live off the dyno)... I think the same can be said of most the modern motors at this point. I would love to see that 500hp set-up though, there are probably a lot of good things to learn there. :)
Honestly, he could do it NA with nitromethane/methanol... but that's going to be a fun learning experience. And by fun I mean second mortgage kind of fun.