Erm... we already can do that. The JIT code has been leveraged to emit native object files, and there's a bytecode->C translator that generates compilable C. (That's been in there and working, on and off, since the first few weeks of the project)

There's definitely a performance win to doing it, though how much depends on how much of the code uses the low-level types instead of PMCs, since the C optimizer has more to work with there.