For neatness, I'd still buy a kit and have it not as neat and working almost as well.. after all, it's the same motor and battery I get.
And if I was to spend over a grand on an ebike, I'd get a nice branded bike such as the Cube or Whyte bike with a BBS02 and dolphin battery. I'm pretty confident I'd be happier with this configuration than the Oxygen.
It will be potentially faster with the right gearing, ability to climb hills properly, great balance on bike, no need to worry to change flat tyres on rear wheel...