1. Arab tree. An Arab tree is generally made with a medium wide angle in front and a very quick twist to almost flat across the center of the back. I have found this to be a good fit on a number of gaited horses. Again you need a saddle that fits the horse and it’s not necessarily going to be any particular name of tree. I don’t know if this is going to work for speedy but it is certainly something to try. There are many companies that make Arab tree saddles it doesn’t have to just be Abetta, which did go out of business at the beginning of Covid.
2 center fire rigging. Centerfire rigging can be a good option for certain horses, depending on where their girth groove is. I would not however consider it an option to prevent girth galling. I have met an awful lot of horses that cannot accommodate centerfire rigging with their particular confirmation. I would be far more inclined to change the material of the girth, and most particular never use neoprene on a horse that gets girth galls. I have two such horses and the problem is fixed by using a wool fleece girth. There are other options as well. Most particularly you need to not girth too tight as then the skin cannot slide smoothly under the girth when the horse moves its front legs.
3. Australian saddle. This can be an option, and is a very good option for horses that do better in an English tree than a western tree. No it cannot be center fire rigged, but the rigging already is farther back from the front legs than a typical full rigged western saddle. I would actually recommend a Wintec stock saddle, because it can be adjusted with both a gullet plate and shims to fit a wide variety of horses. Not every horse, but probably 85%. But you would want someone who knows how to fit WinTec to help you. I personally own three WinTec Aussies and find them excellent options for both a variety of different horses and the people who ride, but that is my situation.