Not 6502 but the Zardoz 65816 compiler from back in the day (early nineties) had different memory models and one of the best allowed you to use the direct page

Not 6502 but the Zardoz 65816 compiler from back in the day (early nineties) had different memory models and one of the best allowed you to use the direct page register (essentially a moveable zero page) to access local variables in your functions. If you made some concessions to how you coded your C, you could end up with reasonably efficient code all things considered. It would be pretty cool to see a C like language that compiled efficiently for a stock 6502.