What if Laser Tower would simply "release" its fighters so that they can follow creeps even beyond range of Laser Tower? You can put a time limit, as the vanilla game does with broodlings (once they are fired they die after a little while if let alone) even for fighters It would work like this:
The tower fires its fighters on the first enemy coming in its range;
The fighters start following thir target and when he dies they eventually move on to the next closest targets, and they keep on doing this until their time runs out;
To make it a bit more micro intensive you could chose to manually activate it or let it recharge naturally. In the last case, once it recharged, it wil fire five fighters as I described just now; if you activate it manually it will fire a limited number of fighters, depending on how much time it cooled down. Or, if you prefer, it could work as Carriers do. Once the fighter dies (because its time ran out) you can manually "buy" another one from the tower (with no money cost, just a cooldown on the skill); tho, if you chose not to buy any fighter, it will recharge on its own, slower than if you manually checked on it.