Please don't take this the wrong way; it's not your fault for not realizing that Flamers and MGs are useless. It's the devs' fault for having useless weapons in the game.
If you actually want to deal damage, or be effective, flamers are not the way to go. They do as much damage as a machinegun (next to nothing) at 2/3rds the range, and create a lot of heat for you. They look cool, but they are currently useless.
In the same vein, Machineguns are currently more dangerous to you than to enemies, because of the possibility of ammo explosions. And even then, for the 1 MG in your build, 1 ton of ammo is more than enough. I don't see anyone needing 2 tons until they have 4+ MGs (or the MGs are a main weapon for the build, for whatever reason).
ERLarge Lasers are currently underpowered (too hot); you'd be better off with regular Large Lasers. The difference in range is barely noticeable, and anyone out of range of the Large Laser will have an ERPPC with even more range than the ERLL anyways.
For the Catapult especially, you should get an XL engine as soon as possible, if you can afford it. The Cat has a huge CT, so you're probably going to be dead well before you even lose the armour off your side torso.
Here's a
similar build, with the same engine:
CPLT-K2
Here's the same build as above, but with a much improved XL engine:
CPLT-K2
But if you absolutely insist on using Flamers and MGs, Why not go all the way?
CPLT-K2