Simple Plan. Mid-Long Range Engagement with those Big Guns. You fire right! You fire left! You fire the AC20 and wave it all about! Gauss Version, Longer range, Better cooling, a bit lower in armor.
AC20 version is the same as my Misery Lost one further down the page except I have a Std 280 instead of Std 275.
Strip the LA's armor, fill it with 10 slots of 'Endo, ???, profit. You're going to want more than 29% cooling on a brawler, which is what any mech with an AC20 is, at least partially. 2 ERLL rides the heat line, even with 17 DHS anyway.
Hard to go wrong with AC20 and an array of lasers, on any mech really. The exact mix and match of which lasers and their placement is pilot's preference on how they want their mech to operate in the field. I think you could even bump that ERLL to an LPL and be all close range. Or 5 ML and run super cool. Or 5 MPL and lurk in dark corners. Or some wacky other combo!