As someone who cares about the Iberian breeds, I wholly disapprove of “breeding for dressage.” I think that’s about the stupidist thing one could possibly do. Firstly because Andalusians, in any event, are bred for dressage. They are the original dressage horse and no warmblood could ever do a piaffe or passage like an Andalusian and certainly not the high school movements. The Andalusian and the Lusitano are old, classical breeds and should be preserved. I think it’s disgusting to ruin a fabulous horse by trying to make it into something it is not. If you want a warmblood, buy a bloody warmblood.
Secondly, if all you care about is the score, then get a horse that can get the score even with a no good, moronic judge who is going to judge your horse on the basis of his or her prejudices. That is by far the most sensible and conservative way to go. That being said, every show is organized by someone - if a judge is biased and enough people complain and say that they won’t ride next year, if that judge is back, the judge won’t be back.
Thirdly, a dressage test is an accumulation of points. Warmbloods are a hodgepodge of different stuff, some of it Iberian. Most warmbloods have a harder time collecting and very few have a truly good piaffe or passage - they might get good scores, but that’s because it’s the norm of what the judges are seeing and simply can’t stack up to what you would see a well schooled SRS horse do for instance. Baroque horses are great at collection and have a harder time with extension. Therefore, if you have a baroque horse, it makes sense to emphasize the parts of the test that call for agility and collection and to ride with a great deal of precision, which is also much easier to do if you’re on something nimble. If you ride intelligently and strategically before an unbiased judge, you should get good scores.
Last, instead of breeding Iberians for dressage, if you want a horse with extension and suspension, it makes more sense to cross breed. That’s all the warmbloods are after all any way - a foundation breed or type selectively outcrossed to produce a given result.