Thanks for the pointer. Basically, Trevor wants the distraction of low-level tweaking so he can think about the high-level problem. That's the weakest argument for low-level languages I've ever heard. But Python fits the bill: Python for high-level, C libs for performance and low-level tweaking.
The big solution I was thinking of would have to go a bit further than Python/C. Basically you should be able to write a description of the actual essential functionality of a program without going into data structure and algorithm implementation that isn't relevant to the problem domain. Something like Prolog or Haskell here, Python isn't all that declarative compared to them. Then you could write the bits that need tweaking in a lower level language, but you should be able to automatically verify that the low-level implementation matches the high-level description, at least through extensive QuickCheck-style automated testing if a full automatic proof isn't feasible. You don't get anything like this with a Python/C style solution.
I've ended up with that style. The robot software is Python at the high level, C++ for low-level or OS-specific stuff. It runs fast and is easy to hack on
