Btw I noticed that I didn't really answer your question about runtime mesh creation. The problem is that the tool isn't structured for that at all so most functions are in the editor scripts. Some stuff probably can be moved but there are still 2 problems:
1. Classes like Bezier are used which don't exist at runtime so I'd have to create my own classes to replace those (totally possible).
2. Editor functionality is so nested into the methouds, what I mean with this is take the create point methoud for example. It changes editor handle ids of points which is located in the custom editor class. It becomes complicated.
So it is possibility but would require quite a bit of work.