It will be replaced by something with a lot more scope.
(Das entsprechende deutsche Topic ist hier.)
Capital ships severely suffer from... their own size.
When the ship is 4km long and a turret battery is spread over such an area then a small "anti fighter" laser with maybe 2km range can't possibly work because few turrets could even reach out to the target.
Also, fighters attacking a huge ship often break before even getting into range of a "useful" and fast anti fighter laser.
As a result capital ships fare terribly against fighters.
I wanted to change that without upsetting the general laser balance or OOS combat. And it worked! =)
- Capital ships have access to heavy laser variants.
- Real capital ships with an actual size of over 1500m will be able to use the regular as well as the new heavy lasers.
(Custom ships are often mislabeled as M1 or the likes so ship class is not a good criteria any more) - Lower rate of fire but higher damage.
Damage/second stays the same but fewer bullets help with FPS and definitely add to the feel of using heavier lasers. - Bullet speed increased by 50 %. This also increases range by 50 %.
For huge ships that can not be seen as a great bonus. This offsets the far greater distances that the bullets have to travel from turrets that are spread out over several km. - All heavy lasers are XL cargo - even the [H] A-IRE.
- Compatible with every kind of vanilla or modded ship and turret without adjustments.
If a turret can use A-HEPT it can also use [H] A-HEPT. - Compatible with XTM (I think =)
- Which ships can actually use the heavy variants is controlled by scripts but I suppose it will be possible to cheat this system with some creativity. Not really my problem, though, if someone considers this fun... =P
- An AL plugin enables all AI capital ship in your current sector to use these lasers.
Player ships do not. This is to avoid conflicts because this kind of laser switching should be left to turret scripts. - There are several turret scripts out there but MARS definitely makes use of Heavy Lasers.

Installation:
Basically, copy all contents of the ZIP into the X3 main folder.
Then select the "Heavy Lasers" mod as "the" mod at the X3 main menu or install it as a fake patch.