Why didn't they just put the monocle on the other side of Preston's helmet?
The helmet might not have been designed with interchangeability in mind, with internal wiring or circuitry not being movable. It was a product of the 80's, after all.
If they were expecting an air to air threat, why not deploy fighter jets, which are actually designed to engage and destroy air to air targets, rather than taking a bunch of attack helo pilots trained in ground attack and reinvent the wheel with them? Of course, if they had done that, there goes the central plot of the film.