Another construct that is extremely fast, cheap and can even represent nonlinear and discontinous relationships is the good-old lookup table. In hardware (FPGA) you get one result per clock cycle.
Now, of course, if you can deal with the error and name the tune with just a handful of transistors it could be a good tool to have.
It might make more sense to have a hybrid. Build a CPU that includes a traditional FPU as well as a "physics-based" FPU. Then the programmer can decide which way to go by trading off between accuracy and deterministic behavior against speed and errors.