For the fire rate of the Light Pulse Cannon, have you considered just upping the load time of the larger weapons? In other words, instead of the base load time for all weapons being 1, make it 2 or 3... then you wouldn't even have to mess with the accuracy bonus, you'd just set the LPC's load time to something smaller...
edit: this would also help ships survive longer in combat, making such things as shield regenerators and boarding parties (not to mention just plain maneuvering) more useful!