No real problems just hassle.
1. You get the bike and do SVA. This usually means finding an smaller/rejetted carb and restricted exhaust to meet emissions legislation. You'll have oversize indicators, mirrors, a fuel filler fairing, smooth mudguards, folding pegs and a left dip headlight to fit as a worse case on the other regs.
2. You can now insure a grey import, in itself hassle, but not impossible.
3. Having got it through all the legal hoops you can put it back to stock and plod and the MOT men will probably never notice!
Kawasaki won't do it because they have to sell exactly what they type approve. With the exhaust bunged up and some hideous new plastic bits the bikes wouldn't sell, so you can understand them not doing it.
Andy