Came here to post the same thing as
@Sideshow .
Very easy to install a switch that could run the fans anytime you want .just separate the circuit from the LEDS. Only thing I'd worry about is you putting it onto bloom and forgetting to switch fans on. Sounds like you want fans all the time though? So wouldn't be an issue . If you're going to the hassle of splitting them apart though my preference would be having control of them via switch mounted on the casing somewhere .You could even have a 2 stage switch if you wanted which would kick in one fan on first position then next fan on second etc if you want to get that kind of control. If you're not electronically minded I'm sure you have a mate who is .? really simple job that needs hardly anything apart from a switch ,solder and decent wire.
That's a lovely plant in the pic . Props to you for growing that

Go easy,
W.