Common Gate Level Shifter
As you note, the circuit as drawn switches "on" much more quickly than it switches "off". 

If you wish to make it more symmetric, simply add a single resistor (say 100K) in series with M2 gate || C1. Note that, to save space, you could use a small SMT zener and a dual MOSFET. The 1N4148 is rated at only 200mA, and you might want to use something beefier such as a small SMT 1A Schottky rectifier (for example, a CDBA120) if you're switching heavy inductive loads.