well, I proposed 3 tons so that you could pick 3 possible ways:
1) Full NARC - avoid brawling, pure NARC platform above 300 meters - below 300 meters it can defend itself well, but only for limited time... should be enough to escape towards friendlies or get rid of light mech.
2) Full LBX - you are decent brawler, for long battles you switch to single-LBX fire
3) LBX & SSRM - another decent brawler set
4) LBX & NARC - I guess it'd be most common setup - nice for brawling & staying far away from base.
This way within one config you have few possibilities & you can become VERY good NARC platform.
Why I picked Bushwacker? Cause it's damn huge, so it won't be anything like "impossible-to-kill guy with endless NARCs" - A4s or PPCs/Gauss/UACs/ACs would get rid of it easily (note: all it's weapons but NARC have 300m range)