Heck, JUSTIN MORGAN< the founder of the Morgan horse breed, was a grade! They aren't even sure today who his parent were, though they're pretty sure. He was part TB, half Arab, and who knows what else.
Now, with studs now days, its good for them to be registered, but with mares, if the mare has everything listed above, and is bred to a nice stud, even if grade, whats wrong with that? It would be a better registered stud, but its their decision. Even if the mare has faults that can be bred out, people say no, and say to just get a foal at an auction, but the reality is, its hard to find good foals at auctions that have everything you want, like to be a Registered Morgan with excellent conformation and such, for a cheap price, depending on your area. Not that is is always hard.
This is just MHO, and a friendly debate! I was just thinking........ I know many will disagree with me, and please forgive me if my thinking confuses you, I got bucked off and have a concussion so im kinda confused :) lol