I like it. The idea of the Republic using droids makes more sense to me, since it’s more humane than using clones. I’ve tried doing my own prequel rewrites before, and I always got stuck on how to define the connection between the clones and the Mandalorians. Your idea makes sense, though I want to hear more about these Clone Masters.
As you are aware the PT introduces these other powers within the Republic: The Trade Federation, Banking Clan etc. The Clone Masters are one of these; geniuses when it comes to genetic engineering
-Maybe they create supersoldiers
-Maybe The Mandalorians, in their later years, are these supersoldiers
-Maybe The Republic rejects them when offered by The Clone Masters to replace Droid armies. Then the Clone Masters decide to take over the Old Republic. Or…
-Maybe The Republic was always based on clones and The Clone Masters revolt when the Republic plans to replace clones with droids - essentially putting The Clone Masters out of business.
Many possibilities 😃
I think I will name the species the Clone Masters belong to as the Spaarti.