That's the Ecomat, which is a great transmission, but its huge and heavier than an Allison VT730. Also fully electronic, and expects a fair amount of data from the engine to work. ZF have a number of different tailshaft angles and configs for it, and if you used a lighter engine, like a Cummins 5.9, it would THEORETICALLY work. but that's a whole lot of engineering to hang that from the roof of a GM coach (yes, that is how the engines are mounted,) and make it work at all let alone be a good set of compromises. The factory package from the 1950s is already a good, proven and durable set of compromises, so the bar you're trying to get over is very high. Worst of all, you're starting with about $50k worth of stuff (built on different continents in different centuries) on a major undertaking that nobody knows anything about.
To get from the back of a napkin sketch to driving it down the road would take YEARS and the likelihood of failure is very high. That's something to do if you already have a serviceable bus you like and use, and you want to prove something to yourself or the rest of the world. As Crown Guy wisely says, if you want to use it, just buy a nice example with the best available equipment and go from there.
