would it not be possible to install reflective devices
Maybe. But that might give the miscreants some feedback on their aim. And some people might just get a kick out of being 'flashed back' by a passing airplane.
Blue flashing lights outside the front door
If that works reliably. What is the arrest rate for l@ser incidents? Unless you are dealing with some abject morons who keep lighting up successive planes, by the time one is reported, they have turned their pointer off and gone inside.
Something needs to be done to ensure that detection and arrest is nearly certain. Possibly a detector (camera) and GPS position that could automatically forward source location data to authorities on the ground. An iPhone/Android app on a phone positioned to look out the cockpit window might be sufficient.