Can ALL Towers be laser towers before 15 minutes?

I don't think that would buff their damage, it would decrease it because it takes time for the damage to ramp-up with the laser, whereas with the single shot it deals a burst damage shot that deals a chunk of hp, so even getting hit once with that shot can literally punish an enemy trying to be thirsty. I do think though that the laser might clear minion waves faster, but I honestly can't guarantee that, that one's just a 'feeling'

I understand what you are saying about buffed damage, however it is much harder to take cs under a laser tower than to a tower that fires shots. This is really hard for players that have fed, as often the only way to farm is under tower. The game is already penalizes players for mistakes, and making all turrets laser turrets would increase this factor.

I think the stronger buff here would be for target acquisition to happen more frequently, even if the delay on firing shots is still there. This way, there's more of a sense that the tower is actually doing something during a dive than continuing to mindlessly aim at minions.