Just a little something I have been playing around with. Surprisingly it is working really well for me. I have been averaging 650-750 points per round with this build. The armor is backed off quit a bit to allow for a couple extra tons of ammo so I have been staying behind the main lines or flanking. I will get off between 2-5 volleys before people notice me and I have to move to the next location. If you drop a ton of ammo and a ML you can swap the LRM10 out for a LRM15. I haven't tried small lasers in place of the ML's just yet but I will give it a go in the near future. Sorry if someone else has already posted a build like these.
900 missiles for a 10 tubes launcher, I think you can safely trade one ton of ammo for a TAG. Let's be honest, your LRM alone won't do much. That way you'll help the heavy LRM boats focus on the same target. Also, you should add so armor on the legs.
I tried something similar Enileph. I just didn't care for the single shots coming out of the right arm. I was running a LRM10 and LRM5 with that build.
I think that this is more balanced: It has enough ammo, enough weapons, enough speed, and enough armour, to help ur LRM-boat fellows, hunting down enemy scouts and so, while giving them ECM cover to avoid counter-artillery.