Number one, check this out with his Scout Master, who will have lots of ideas on this subject. And, if like my Scout Master DH, then he will also have masses of books about every subject that the boys should be taught. Or the mothers of the boys who do have the jackets. It's highly unlikely that the boys themselves have made their jackets. You could get their names and addresses from the Scout Master, after he has asked their permission.
My late DH was an Eagle as were his two brothers, and our son.
The order of the Arrow is an honor, so I'd suggest that you also include the arrow somehow in the jacket, maybe where a breast pocket would be and/or on the sleeve. It's been so long that I've forgotten what what goes where. Check it out on the Internet for different pictures.
As for the Seminole quilting, there are plenty of patterns around. If you can look at something and copy it, then just pull up some pictures of it. It's more or less just strip quilting, and I think that Bargello might have evolved from this style. The Indians used the left over strips of cloth on the expensive and hard to get bolts of fabric, not wanting to waste anything. Then, like women everywhere, they made a few changes by cutting and sewing them together again, competing with each other.
You could get your son's input on colors and directions of the stripes, and show him samples pulled from the Internet. If he is as strong minded as my son is, then he will have his own ideas about color at least.