I've been a programmer for a very large portion of my life and have to say that I, personally, don't feel that code is an appropriate way to express 3d shapes. This is in my opinion of course.
For you, given your obviously gifted talent for this sort of thing, it might actually be much much easier just to have a software interface. I don't thing most of the population is like this.
I'd say for most a visual graph display is more natural a conversion of our ideas to shapes then text is. That combined with the live updating models and you've got yourself a winner.
For the more technically inclined you also get to play around with ADDING blocks (via the script block) which is a perfect bridge between the technical side and the conceptional side.
As for features, I'd like to suggest a few things that might be helpful.
For the node graph system, I'd say take some ideas from Unreal's UDK.
1. Comment Blocks that can be dropped around large block groups
2. Ability to rout "cables" the way you'd like (Snap to a "junction" then to where you'd like to take it)
3. Select colors of wires.
4. The ability to collapse and expand XYZ from floats to a Point object (making it a single value) for nicer routing.
5. Variable declaration
Outside of that, something that would be interesting for larger scale design, it would be nice to be able to load multiple "mini-projects" into one larger project. When designing an engine for a car it would be nice to be able to make every complex shape it's own project. From that state you could import it into a larger complex project to fit all the parts together how it should look in the end.
That alone would be a massive undertaking. But my begging hand is still out: I'd like to be able to "simulate" what will happen. Adding this feature takes your project from simply being one of the best open source CAD projects I've ever seen to being one of the best cad projects I've ever seen. For me rivaling the usefulness of Fusion 360, Autodesk, Creo, the likes.
Aside from that, maybe add a more traditional interface in which I can right click on the model and say "3d->extrude>cylinder" and visually in the model edit the project while also changing the node graph.
I've got to say this if no one else has told you this yet: you're on to something big with this software and I DO hope you keep it up. You're building something that will bring engineering into the hands of us mere mortals. Coming from CS it's crazy to find the huge lack of open source tools and documentation in this space that you are seemingly fixing single-handedly.
Keep up the good work! Well, I should say the amazing work!