_ Not quite a piranha, but not an ice ferret either. Max Engine to make the most of the few advantages you have. 4HML pack a punch and supported by a few DHS they should do well. 4LMG are in the same range bracket and add some heat-less DPS.
I run a similar build with regular MG's and an XL270 and I love it. I will definitely give this a try. Are the LMG's worth it over the standard?
LMGs are quite good, but after some nerfs it comes down to personal preference whether you run light or regular. I prefer light because they have the same range as HML allowing you to play safer. They're not the main DPS weapons, rather a heatless 'boost' for when the enemy is opened up or your heat is built up. If you prefer higher DPS over the range advantage, go ahead by all means!
5/5, I run this with the stock XL170. Is very effective, the high mounts make for great peeking and the dead arm and 2Hml in the right arm make for a sword/shield combo that is very useful.