Here's the plan:
Shapes will be created with the mutation engine (first version done: to be rewritten incorporating variable data-sets)
you can have separate shapes: copy, paste between them, or adjust them individually, including the size of their data-sets...
Spore had an interesting way of attaching parts, but it was limited to preset attachment points. Shapes should merge at overlapping or close points, and detect whether the triangles should flip to prevent a mobius effect... ...(and whether the shape should connect at all)... also deciding if internal triangle-sets are removed (since you don't see them anyway)
Each shape or collection of shapes could be a "Part", and to save these parts in such a way as the program will recognize them as building blocks (to be modified at any time), and that they are all auto-loaded into the program transparently...
The core of the program is the mutation engine, without that vital feature, you're just playing with legos!
The best approach is to have a combination, silly-putty as legos!
...how about auto-greeblies...
The PERFECT mesh-generator would be the Asgard console on Stargate!