What would you like to be added?

A way to obtain double-precision parameters about CelestialBody objects

Why is this needed?

Parameters in the CelestialBody class are represented internally in KSP via doubles, so I don't see why not to expose that level of precision via kRPC. For backwards-compatibility, new procedures could be added which do the same things as the existing parameters but returning double instead of float.

I think it's ok to just change the existing functions to use double, and break backwards compatibility. Clients like python wouldn't really break (due to their type system) and clients like C++ would at least catch the change as a compiler error.

If you'd like, I can make a PR

Yes please!