I thought about it when the new Trumpy's first came out, Ken McIntosh in New Zealand builds excellent Norton wide-line repro frames, and an engine from a modern Bonneville wreck wouldn't be too expensive, but Triumph have pretty much covered it with the new Thruxton.
There's also a company here in Oz building a Triumph based "retro-racer" with alloy race tank and fairing etc, I'm looking forward to seeing one in the flesh!
Here's a pic of the Thruxton, to you guys who've only seen "American" Cafe Racers, this is what a traditional Cafe Racer looks like, you'll note that there's no "clubman" bars, poxy 16 inch Harley back wheels, or chopper "drag pipes" etc in sight, ha ha!