The laser range on a power of 1-10 MW.
The strongest military laser today is around 1 MW, while many average only around 100 Kw.
Now, your lasers are thus more powerfull, and they fire much longer bursts. A 10 MW laser will penetrate most armor.
Speaking of which, all these lasers are chemical. So they should have ammunition. Might rebalance that actually.
As for the Gauss gun, currently it's noted as a weapon that fires heavy slugs at supersonic speeds. It will pierce the armor of most things it hit, and if it doesn't, it's will knock them back a few meters and ensure their armor is utterly broken.
I can change it to being a supersonic version of a machine gun, but that will reduce it's impact quite a bit.
Now, onto Kevan. There are things I'm willing to accept, both you having a self destruct trigger (which sadly, due to the nature of a Nuclear engine, will do little more than FUBAR your mech. Nuclear reactor =/= Nuclear bomb, after all), and the UGV system that works using a chip inserted in your brain. (Which you know, would explain a lot).
That does however mean that if you're ever find yourself separated by something that would block radio signals, including being more than a kilometer or something away, that your mech will self destruct. (brain based radio transmission has terrible range. Something to do with not boiling brain cells.)
On a side note, you guys do know that you are going to be destroying a mercantile vessel, right? And that your job is to trash the hangar bay. (Also known as the place where, hypothetically, the evacuation shuttles would be located.)
I have a series of reasons why they're utilizing you guys though. Mostly them being quite desperate.