Total agreement here, Ronin...that Model D really has no place in a small cab of that sort...or, potentially, any cab. Consider that a Minimoog (which it's a copy of) is actually a very simplistic build, one which these days could theoretically be assembled in Eurorack in half the space of the Model D (or less!). Leave it in its own case where it belongs, use the space for something more productive.
As for that, again, Ronin's spot on. There's a serious, crippling lack of modulation sources, VCAs, timing/logic, filters, processors (pretty critical for ambient!), mixing and utilities. Stop working in this direction; instead, take some time to explore what other experienced MG users are doing, as well as looking at classic modular and patchable synths to see how they're designed and what implementations those designs help create. VCV isn't a bad idea, either...start with emulating something basic such as the Minimoog architecture in it BUT with the patchability that modular allows. See how this functions on that simple level...then begin experimenting with how to extend that. Translate the results into practice builds back here in MG. Also, examine what artists you enjoy and respect use, how they use it, and again how you can build onto that to make something that's very much your own.
You won't nail a design in 'one' unless you do massive research, and even then, it would be a real fluke to get EVERYTHING right. Make mistakes. Make lots of them. Screwing up on MG = no money lost. Not so much so if you try this with real hardware first.