Over the years, due in part to the rarity of the breed, people have attempted to re-create them. I've done it, too. Satin Angoras are another breed often subject to crossbreeding. While not a bad idea to bring genetic diversity into the breeds, and to improve body type, many breeders have had issues with "wool depression" in the early generations.
I used Tans to bring the Tan Pattern into my Giants. Those early generations definitely had issues with molting and wool block (not to mention temperament!). However, when I bred Thriantas in, I did not have the wool block problem, although they did molt. Nor did I experience it when I used fuzzy French Lops (the wool gene exists in the breed). Why, I wondered? I know at least some people have also had the issue when using New Zealands and Satins.
I *think* the answer has to do with flyback vs rollback coats.
My *opinion* is that breeds with flyback coats should not be bred into angoras except for terminal crosses for meat. Or, the best shorthaired babies should be kept for breeding and the wooled babies culled for at least a generation or two to give the gut, which seems to be narrower in breeds with flyback coats, time to expand.
Breeds with rollback coats have longer hair, and they molt, and I believe their guts have adapted to it. Now, I have no scientific evidence to prove this, simply things that have been discussed between myself and other angora breeders who have had experience with crossbreeding.
Brian Hartzell agreed with me on this, and he often stopped me at shows to ask how my Giants were coming along. When he judged some of my 1/4 French Lop. 3/4 German "Giants", he got even more excited that I was about them. I'm not exaggerating, I have witnesses, lol.
So my recommendation is, if you want to crossbreed because you're having difficulty finding good examples of your breed at an affordable price and within reasonable driving distance, it's not a bad idea. Just think about these considerations:
1. Don't try to pass them off as purebreds unless and until the crosses are off the pedigree
2. Use breeds with rollback coats if you can
3. If you can't, wait at least a couple of generations before you start keeping wooled babies
4. Select for non-matting coats that don't molt
And just a couple more thoughts:
1. For Giants, select a breed that has heavy, not medium bone. Ears and shoulders are easier to breed out than sore hocks.
2. Wool has more points than type.
3. I'm not being critical of anyone, just passing on information that may or may not be helpful
4. If someone you know has already crossbred in the breed you are interested in, by all means take advantage of their hard work! No need to reinvent the wheel!
That's all, folks! :)