By request:
This is based on beta numbers so it may change. But if you just want to design a cheap laser boat (or missile boat / gun boat), and you don't mind small engines / slow movement, this chart will help you get the most usable tons for cheap, to load up with weapons of your choice (hardpoints permitting, not that we know what the hardpoints will end up looking like yet).
"Usable Tons" means the sum of all armor, weapons, heat sinks, jump jets, or other equipment you can add to a 'Mech. This is how much is left after accounting for the weight of stuff you can't remove including the engines, gyro, cockpit, and internal structure. So you wont find a lot of big-engine, speedy 'Mechs at the top of this list. This does, however, reinforce what everyone already knows even if they won't admit it: that Urbies are #1 and nothing else comes close.