I originally came up with this as a variation to Blagg's ultraman. He suggested I post it in a new thread, so here it is. It might end up being a bit slow, so you could always trade a couple of tonnes of ammo + a heatsink to get the STD 300 engine back. That might be the best option while you're leveling the chassis as you won't have the advantage of speed tweak and 2x basics.
Drop the mediums and AMS for another LLaser? Heat efficiency is still good, you could even drop another HS to shore up the armour.