They came out with these many years ago, 60s, I think. You still need a gear on the cam at the back to drive the oil pump. I think that there was a dummy distributer shaft for this.
The theory was that the cam driven at the front would flex and the timing would be out at the rear where the distributer was being driven. I quess that advancing the timing a bit to make up for this wasn't simple enough.
Needless to say, they didn't take off......................