Custom half shafts - supplier?

[minimutly]

But in reality, what sort of market would there be?

Not massive I would suggest. So paying a proper wage for that apprentice, even a keen one, especially when he becomes an ex-apprentice would be hard work. And if you aren't paying a proper wage, or indeed, even if you are, how does that ex-apprentice buy the business, buildings, machinery etc, knowing its going to be long time in debt?

And if you bung the price up to sensible levels to support a young person in debt . . . all you will get it complaints that the old guy didn't charge that for his, and the bloke down the pub said his mate just cut n shut and welded some up for someone and they've been fine in a 5000bhp monster the last half-century . . .

So we're all doomed then, caught between big pro outfits and old farts doing stuff in their sheds, whilst the government gives India bungs to improve training and tooling so their hard working and sandal wearing youngsters can buy a bench so they don't have to work on the floor....