Maybe skip the arm laser in favor of a TC 1? Thinking about it, we could do both by switching to a LE 280:
It's still a more than OK-ish buff to the range and projetile speed. Easily worth 1t + 1 slot. I'd mount a Laser-AMS if you still dislike the TC:
I'm on board with LAMS, range is plenty, can also go for 3ERML because it's such a heat efficient build. (LBX5s theoretically deal optimal dmg up to 850 m in my current skill tree, but due to the spread the effective range is lower anyway)
Still running the LE300 version, and it has been kind to me even in Faction play glad that LB5s are here for the IS nowadays. Screenshots from stream soonish.
This is my current iteration of the build. Works pretty fine. Armor values are actually very workable thanks to generous armor quirks. You can skip the AMS all together when in need for more LBX ammo.