that... about sums up my emotions on the subject. Admittedly, I have a somewhat limited exposure- I board at a mostly gaited barn, don't have a gaited horse but have ridden "pure" gaited horses and mixed gaited horses. These are usually TWH crosses as well. Most of these are unknown crosses, and sketchy breeding, so I can't say what would happen from two well conformed horses, but in my experience:
-"mixed" gaited horses usually had difficulty differentiating from their flat/running walk and trot
-"mixed" gaited horses have an easier time 'learning' to canter or becoming more balanced at the canter, but
-"mixed" gaited horses may be encouraged to trot more as they canter more
-"pure"bred gaited horses usually have an easier time balancing themselves, i.e. carry themselves a little more
Now, please note the paragraph above my bullet points. These are not facts, these are experiences, and definitely does not define all mixed bred gaited horses, mixed bred walkers, or pure bred gaited horses or walkers. Especially since my experience usually involves conformation that may hinder their gaits.
Furthermore, breeding is a crapshoot to begin with- you can hope that the foal will inherit the best qualities of the parents, but there are no certainties.
I would probably not breed gaited to non-gaited. If I want a nice gaited horse, then I would purchase a nice gaited horse. I guess I am in the camp of no nonsense breeding, period. If I was breeding for a gaited horse, I would want the best chance for it to inherit good conformation which would lead to lovely, balanced, natural gaits, which would mean two well conformed gaited parents.
Sorry if that's confusing... but you wanted opinions, right? (: