A maneuverable brawler with reasonable heat management. You can spam the medium lasers 3-5 times before heat becomes a problem (depending on map and efficiencies). At that point you can lay down cover fire with the AC/10 while you break contact and cool off. If you don't have the cash for that XL400, you can use the stock STD340 with reasonable results. You do have to drop a heat sink, but you gain a half ton of leg armor.
I just don't think that this Battlemaster brings sufficient pain to the battlefield to justify its tonnage. With a bit of tooling around, I was able to make a Hunchback that fits the same profile, less an MLas, AMS, and 35 tons. Same idea, but with a Blackjack. It's missing nothing and it's 40 tons lighter.
with the only big difference of Cool Efficiency/DPS and Armor to Brawl. Don't underestimate 6MLas supporting a single AC10. You can kill Assaults within some few Alphas..
Armor speaks volumes! My only critique would be to throw that DHS from the arm into the left torso then drop some of that shield arm's armor into the legs. Any competent light pilot will go for legs first on bigger mechs. Otherwise, it's a solid 40-point pinpoint brawler with plenty of armor and either high speed for 500 points of armor, or, a STD engine... Not a bad build at all, sir! Edit: Oh yeah, and, front-load your armor. If you're concerned with brawling and you're that fast, you need to be concentrated on whats in front of you. Even on an assault, I never go more than 18 points in ST/Rear and 20 CT/Rear. You neeeeed that head on defense against an Atlas or Stalker.
I'll take the STD340 version for a spin soonish. Though, I'll admit, I'm not much of an assault pilot.
I'd drop down to a 325 (3 kph is not that much) and added a LLAS to the arm hardpoint. Then we are talking assault class IMHO.