Poptart variant of the new Griffin 2N abusing the ERPPc velocity quirks. The combination of the high speed, high range pinpoint damage with ECM on a mobile chassis should do a very nice sniper. The whole left side of the mech is there for shielding purposes.
You can drop the speed back down and use the XL for more jump jets and more heat sinks. It's still slightly faster with a XL280 vs. STD275. Used to run something pretty similar on the TBT-5J before they added cockpit shake to jump jets.
Sub Nose is a sweet idea. They are a bit limited range-wise, though. ERPPCs received a very sweet speed buff in the patch, so maybe...