>Nobody would entertain a 10 year old unproven dog
Sadly an unethical person might - particularly if they didn't have to pay, they might think it worth the risk. These are the very people you should be wary of: yes they *might* offer you a puppy in exchange for his services BUT, and there are huge buts in this case, this is likely to be the sort of breeder you'd ordinarily avoid like the plague!
I know that having a puppy from your lad sounds very appealing - the truth is that you are likely to be able to get exactly what you want by going to the same breeder, or similar lines, or even just a very good breeder with dogs you like. This way you'd get to choose the puppy and temperament that suits you and your family. Imagine being in a situation when you've mated your boy with a poor standard of bitch (as this is the type that may come to you) and you have to choose your next dog from a small litter of not terribly good specimens. You'd feel obliged to have one - but it may not be what you really want.
I know I'm painting a negative picture but at 10 years old, and with no history of show results to demonstrate he's a good example, your lad isn't likely to get his pick of suitable mates. It's also worth thinking about what you are expecting of him. A hip score at his age is probably a procedure he won't benefit from and by the time you've got results and found a possible mate your lad could be at least another 6 months older. You have no experience of mating so it could be very stressful for him, to say nothing of possible injuries. It's far from being an easy process and nature doesn't always 'take it's course' !!
Just buy a puppy instead - it'll be cheaper in the long run and much safer for all concerned. Sorry if it's not what you really wanted to hear :)