To add to the original idea...
I take care of an Appy from the original stock (she has the marking on her papers and everything), so maybe that sways my idea. In my experience mixing breeds with the Applaoosa has done little good for the breed. I really don't care if people decide to do this, but I'm going to steer clear. I somewhat fear for the future of the breed, but not enough to ask for more regulations on the breed.
My reasoning for not mixing is because Appaloosas naturally are very intelligently bred horses. They have their akward fram and little mane and tail and this deters people, but internally they are very hardy animals. Appy's are known for their sturdy legs and tough hoofs (very necessary), little hair (convinient in some occasions, though looked at as ugly currently), endurance, agility, flexibility, and just the ability to last a long time. I have experienced all of this with my mare and read much about it. On top of that Appys are known for their attitude, something I love. It seems to me a result from their intelligence. They are very smart animals and if you have a good relationship with them are usually a wonder to train at any age. Now, lets talk of QH Appys. They usually look gorgeous, but I have witnessed on numerous occasions their poor leg structures. Many become crippled at a you age and do not move a fluid as appys. This is just a quick example of what the mixing can do.
Anyways, I will stay away from mixes no matter their beauty. I like durability in my equine.