[sfpotter]

You're in luck! As of a year ago, I work at McNeel on the math team on Rhino's in-house CAD kernel. Luckily, we own the entirety of the kernel, so we are free to improve it. I've been in the field of numerical methods for most of my career in academia and industry, so you are preaching to the converted when you say that Rhino's numerics are mediocre. At McNeel, I'm actively pursuing strategies to improve this situation, although it will be a massive long term project.

Hopefully you know that you can reach out to the McNeel developers directly and on the Discourse forums. But I would also love to chat directly if you're interested. It sounds like you're working on a project that is both sophisticated and interesting, which directly stresses many of the known pain points in the kernel. If you're interested, I can shoot an email to the address you've got listed in your profile from my McNeel email.