how much money do you have? It would be hard to do since the frame design is totally different. And the 9 frame is probably too narrow for the wide motor. but who knows.... I would be curious to see one...<img src=http://www.ezboard.com/intl/aenglish/images/emoticons/embarassed.gif ALT="">
I would contact Spondon Engineering in th UK. They do specialty frames, and I am sure they have a smaller wheelbase aluminum frame that would be up your alley. I was planning a Spondon Streetfighter w/a single sided swingarm, and upside down forks, but I was having trouble finding a good 11 motor. Too much work, so I bought a 12.
Get a ZX-9R and install the Muzzy 998 kit or whatever it is. You will have the weight advantage because the 9R's engine is smaller than the 12's and you will make more horse power than the GSXR-1000! Actually, I think the kit as much horsepower as a bone stock 12R.
I have shoe horned a ZXR900R B2 motor into a ZXR750L chassis and it worked out great. I measured up the 12 for size whilst I was there and it would need a serious amount of chopping and changing of the frame rails!!
I might still have a try next year when things settle down for me and I get some spare time (185 BHP closet ZXR750)!!
Spondon and Harris both will construct a chassis for you but you will have to wait some time and spend big bucks! But you will have something different!
There are lots of other frame builders in the UK, Street fighters list quite a few as well.
Hope it helps you out