My first two chargens

First off, Traits..
12 APP is one fine looking cockroach! Without Erotic Arts or some other mutation to help out APP... Your game, your rules.

Also, 18 INT is very smart for a cockrach at R1. Maybe he's not the fastest thinker, but that WILL of 58 means he studied Robot books/videos until he learned the skill. (I don't think he'd be illiterate and a Robot Technician, but that's just me.)

108 STR is awesome at R1! Yeah, melee weapons, fists, mandibles, etc, all recieve +16 damage. TME bottom pg 10, (**Strength..)
(For my games, I consider if the tool/weapon in question can take that amount of extra force. If he hits someone with a pool stick using all of his might, it's definitely going to break, in my game.) If the crossbow is set to your STR, not many other people will be able to load it.
 
44 END is great at R1. Keep in mind that the "average" (PSH) character Trait is 25. This isn't a 100 pt scale. This is a '25 is average' scale but you really don't have modifiers unless you're under 10 or over 34. Nothing wrong with 44 END my friend.

-41 DV is going to help keep him alive for a while. Without bonuses, R1 characters have a 1-50 SV. It will take some skill or a lucky shot to hit him, fully armored.

Here's my take on Knife Fighter skill and this guy>
Normal 2 armed, "one dominant hand" Knife Fighters get 2 melee attacks/rnd.
Pg 27 states cockroaches have "2 dominant hands.. can use 2 pistols, 2 crossbows.." So it's kind of like he's ambidextrous, but not exactly.
Under Knife Fighter, "a 4 armed character.. can make 2 knife attacks/dominant side" (paraphrased). I think he gets 4 knife attacks/rnd.
(Bestial Humans sometimes 'break the rules' in natural melee attacks per round. Maybe it's their primal ferocity or natural weapons, but most other four armed characters don't get an attack with every arm; pg 71, Multi Arm)

Caymus may not be smart, but he just needs a lot more time to putter around in his gun shop. He's not a pro, he just tinkers whenever he can, until he gets better.
TME pg 40 shows what he can build and how many hours it requires. Right now, it takes him a long time to do anything and he's likely to have a few set backs; it's a hobby.

These are great characters! Characters aren't static in TME. They Rank fast and change like the wind. The dumb ones get smart and the weak ones get strong. These guys will look very different after 3-4 Ranks. Don't write them off yet.

I agree with Providence, two very good characters. Don't forget being a Roachman many communities are not going to let him come around, or will at best charge him extra for supplies and gear, at least that's how I would play it. So he needs to be tough in melee, cause a lot of folks are not going to want him around. : )