Well, it needs a tall tank so the pump's side flow doesn't splash everywhere.  Some fine tuning is required to get just enough pressure for a certain voltage without too much side flow.  Once tuned, the PWM value could be hard coded.  An ESC which doesn't constantly beep is required.

The hose fitting for the stock reservoir had the hose stop outside the reservoir, so the water went sideways instead of in the reservoir.  It needs to go all the way into the reservoir to keep water from going sideways.

The stock reservoir was no longer water tight after drilling out the hose attachment.  The original reservoir manetaned a vacuum which kept water in.  

 Without a water level sensor, the pump has to be manually  toggled.  Sensing water level would require a pretty complicated sensor.  The stock tank is too small for any conventional sensor to fit.  A conventional sensor would displace all the water.  The leading theory is to have a custom ultrasonic sensor measure the resonant frequency of the tank.

It is believed the reservoir is as small as it is because the MEMS transducer leaks if any more pressure is applied.  You couldn't attach a bigger tank & call it a day.  A bigger tank could gravity feed into a smaller tank.  

The MEMS atomizer requires 2 tanks, 2 circuit boards, 2 voltages, lots of wiring to the pump & the atomizer, a sensor to manage the water level.   The atomizer & all the plumbing take a lot of space & have a lot of problems, which got the lion kingdom thinking of alternatives.  The leading alternative is an automotive fuel pump

  https://www.amazon.com/Electric-Universal-Pressure-Transfer-Carburetor/dp/B08PY7V2MM

feeding a common mister 

https://www.amazon.com/HOMENOTE-Misting-Nozzles-Outdoor-System，0-0197/dp/B08T17V72R

to atomize the water.  It would require only 1 water tank & 1 pump.  A test with a .2mm printer nozzle showed the printer nozzle with home made pump just squirted.  It may require a lot more pressure to make a mist.  That's why the safest bet is an automotive fuel injector with automotive fuel pump.  They're just expensive.