Hall effect to increase voltage
I'd suggest using an MCU as well, you can still use 1 magnet on the axel to know the train speed (you can average and divide by 4 on the MCU itself) and control the coil from the MCU.
With a PWM (generated from the MCU) you can adjust the power of the coil in the rest and active state. The same goes for the fan.
However, the coil response of a vape is a few seconds, so it might be difficult to do short puffs. You would probably need the more sophisticated implementation to continuously produce smoke.
Perhaps continuously producing smoke in a cavity and modulate the fan speed, with a fast, small, fast response fan, to produce the puffs.
A small arduino is probably a good way to start.