3GE do one,and someone in clydeside is as well.
My idea of a complete chassis would have all the brackets fitted for suspension,steering,rad ,brake lines, roll bar inc and wishbones ready to bolt on.All you would have to do is fit hubs etc (available as a kit of course).
The idea of the Roadster is that " you " build it on a budget and the satisfaction I personally get from seeing a pile of metal growing all beit slowly into a car is indescribable. The day I can say to someone that ask's "Where did you buy it" will not come quickly enough and you know exactly what the answer will be.
There is a market for what you have in mind and something custom built to their spec is what some will be looking for.