I'm going to go ahead and assume you don't pilot lights. Lights (especially low tonnage lights) are some of the most slot hungry mechs.
Six slots from XL Engine. 14 Slots from Endo-Steel. On a Sub 35 tonner 14 slots from FF if you want to actually squeeze some armor on after engine and weapons.
A locust is going to struggle to fit a LL + 4xMachine Guns (the standard 5K build) with its low weight and it certainly won't have the slots to have double heatsinks with it. And as the added kicker those four external heatsinks will be 1.4 doubles, so even if you can somehow fit in the extra 12 slots to have double heatsinks in it you'll lose 1.2 effective heatsinks compared to the 5K.
So yeah, external heatsinks matter. It's either going to overheat with a single Large Laser or be even more weight handicapped by not being able to take FF for the ~0.5 tonnes it'd gain.
Again, forced external heatsinks (my mistake, it's four not three), 20 tonnes, less armor, no lower arm actuators, no jump jets.
Even compared to what is widely considered the worst mech in the game the Locust looks terrible.
Edit:
Just checked, it's not actually possible to run a locust with 4xMG and a Large Laser with an XL170. At least not with anything but barebones armor. Which considering the tiny, tiny amount of armor you can put on a 20 tonner is saying something.
So, biggest and baddest the Locust 1V (the one that you'll get with the 30% CBill boost) will be able to field is a MPL with 4xMG. Can't even reasonably fit a lone AC/2 on it and the center torso energy mount rules out PPC.
Edited by Mahws, 25 June 2013 - 08:15 PM.