This is arcane, but stick with me. I am going somewhere with it.
Back in the 1960s, there was a South American bred horse named
Primordial II who won the Display Handicap at Aqueduct. If memory serves correctly, it was then a 2 1/16 mile stakes race. Yes, in those days the NYRA circuit closed sometime in the late fall and ran some very long races.
Primordial had papers allowing him to race in the US, but not to be used for breeding according to a rule requiring 8 generations / 100 years of TB breeding and demonstrated racing ability. Upon scanning the JC rules, I cannot find this generation/year span rule. Is it no longer in effect?
Primordial pedigree:
http://www.pedigreequery.com/primordial2
His sire's 3rd dam, Hablilla, was a daughter of Vadaukblar, whose female line traced to the Mogador mare:
http://www.pedigreequery.com/vadarkblar
Who is listed as the foundress of Argentine Family 2, and who has no dam of record.
Assuming somehow that this generation/years of demonstrable racing quality rule remains in effect, would it be possible to cross a TB mare with an Appaloosa stallion, retain the fillies with Appaloosa markings, and continue to keep crossing generation after generation with good TB stallions until one had individuals with enough generations/time of TB breeding--and who had Appaloosa markings--who could then be registered as a TB???
This is all hypothetical. I realize how impractical such a project would be.