ON1-K I wanted a ac/20 build but wanted to be able to reach out and touch somebody while closing the distance.
I run a similar one. I have SRM4 + Artemis with 100 missiles instead of AMS. Also less AC20 ammo (21 and not 28). I enjoy this mech ! It is very deadly.
I trade the AMS for a pair of SSRM2 with a ton of ammo. Regardless, 2xLLas and an AC20 is probably my favorite weapon combo in the game. Very good build!
I think just an AC20 and 2x LLas is a serious undergun for a heavy, let alone the heaviest heavy of them all. I mean, a medium can easily do it, really.