
A very male perspective :D
You notice I said get him castrated if they cannot ensure keeping them apart every season (this would appear to be an issue hence the posters question).
If he isn't a really good dog (as you say breeding is about breed improvement) then he is unlikley to help produce excellent pups from the bitch of unknown quality.
If the bitch is of above average quality, then using a top notch sire will give a chance of improvement, breeding average to average will just give average.
Of course the bitch might not be good enough for breeding too, that is why I then suggest spaying her also.
Now if the dog was not bad, and bitch not very good, it still wouldn't help the poster, as no one will want to use their so so dog on their top class bitch to get him a pup that is an improvement on what he has, and they would still have the seperation problem.
If you want to be a breeder you really need to own the mothers. No mater how good a male you have you are at the mercy of the bitch owners as to whether a bitch of the calibre you would like will ask to use your dog. If you own the bitch then you can use the best dogs available if compatible, and then have the choice of which pup to keep.
Like I said showing the pups should at least give a clue as to their quality and which approach is most practical. I am sure the poster will please themselves. :D