Wheel heading using PWM
Yes, this can easily be done. Lets assume the steering inputs are a MUCH lower "frequency" than the PWM frequency.

The pulse width effectively becomes an instantaneous signal, like a voltage. Now you've just got to map the signal to the wheel position. The pulse width can't be negative, so you should introduce an offset to give yourself some space.

Older RC equipment does exactly this. They map a pulse width of 1500uS to 0%, 1000us to -100% and 2000uS to +100%.

Your "wave" will not get transmitted as a frequency. Rather it will be transmitted as a series of unique values (like graph points) that can be used to construct the original wave.