Since this SLS model is intended for high production numbers, I don't see how utilizing existing hardware (like heritage gearbox designs) will reduce costs long term. I agree that adopting a single modern turboshaft engine is a good idea. But it would also be a smart move to design a dedicated drivetrain using the latest technology for this model.
Unfortunately, it seems that the bean-counters at Bell have decided that it is not worth the time and effort to design and qualify a new drivetrain for this product.