looking through this script, it is just a glorified:
Code:
ifconfig $param2 down
iwconfig $param2 mode monitor
ifconfig $param2 up
why not just type that in directly?

or if you want to create an interface or multiple interfaces, just use iw:
Code:
iw dev wlan0 interface add mon0 type monitor
you can do that to create as many interfaces as you want(im sure there is a limit though), just increment the monX number, or call it what ever you want
pretty much all that airmon-ng does anyway