Yes you are quite right when you refer to some of their best stallions and their own high performance mares, I have seen a lot of the Z stallions and ASCA Z is one of my favorites, I watched Harry Smoulders riding Regina Z(I think still with Axle Verlooy?) and what a mare!!!!
I keep looking deeper and deeper at the breeders and what they are looking to achieve, Frank Reikers had his dreams come true with a horse he bred, GIG Amai, ridden to victory at Aachen this year by Micheal Whittaker, no mean feat I can tell you, but if you look at the sire of GIG Amai, Non Stop(Darco x Carneval), this is a very cool stallion, I have brushed, washed and clipped Non Stop, my partner used to exercise him everyday, he was so cool for a breeding stallion we could walk in the woods and I mean walk, the two of us on foot and Stoppy as we lovingly called him walking beside us, even passing other horses was no problem.
Those were horses bred for top sport, but all I ever hear from breeders today is the need for high blood and character for top sport, GIG Amai is a top sport horse but off his head and full of blood he is not!!!! His sire is not exactly a dope on a rope but he has exceptional manners and is well bred for sport of some 22 years ago, but he is still producing very good young horses today.
It's just my opinion that too many people want to breed the next winner of Aachen or gold in the Olympics for the revenue and some bit of glory but with so many others trying to do the same I really do think it a more wise thing that if you want to breed, then breed a horse that could do well equally in top sport or for an amateur to jump in the 90cms classes without trying to kill anyone!!!!