Manyfist said:

"You got your Black Crusade in my Only War!"

But in all seriousness could be a fun excuse to transition to BC

Eh, it wouldn't be that big a mechanical buff to Storm Troopers.  STs are gonna basically have the same protection from Good Craftsmanship Light Carapace that they would from Common Craftsmanship ST Carapace anyway a lot of the time = 6+TB.  (This is also why I think the Light Carapace at Good Craftsmanship should remain on as an option and drop its weight rather than being totally replaced--some players would like that lighter armor and still having largely the same protection)

WittyDroog said:

There's already that option, get 100 corruption points, and ask your GM to transition to BC. Then again, you have to dodge Commissars & higher command. 

 It just seems a little odd to me that you can get Corruption points as a part of the system, but they only have rules for the very minor Malignancies. 

@Plushy

Yeah, but in what case would you actually need more? Guardsmen have very little privacy, presumably thorough medical checkups every now and then and bosses with really low tolerance regarding mutants. Any mutation will remove the character from play sooner rather than later - so why waste pagecount on them?

Could you describe a situation where a guardsman character with a real mutation will remain in play for a longer time?

 Yeah its more an issue that you'll lose characters more to summary execution more than actual combat. You could think about it like this, because of their mental indoctrination and how they conduct other everyday lives they're not going to be exposed to the same chaotic horrors as some Inquisitorial agent digging through forbidden tomes and touching daemonic weapons, at least not on a regular basis…

That's because guardsmen come under much more constant scrutiny than Rogue Traders or even Inqusitorial Acolytes. They are constantly surrounded by people that will denounce them to the Comissariat the second they spot something that shouldn't be, upon which they will get promptly blammed and their corpse tossed to a ditch and incinerated. 

Essentially, getting anything but the most insignificant and hideable mutation would imply the immediate loss of a fate point.

 Feel No Pain, Tough Skin, Big Eyes, and Wyrdling (all from the DH Minor Mutations table) could easily escape notice. As for more serious things, I think having to hide your mutation is good character development and includes several plot hooks.

Plushy said:

Only to casual observation, a Medic takes a look at you for checkup and its stands it out to thier eyes. The only. possible, kind of mutations that might be acceptable are those that both NOT deformed and benefical. While the planet no longer exists, the Homeworld of the Night Lords existed in a stat of eternal darkness and its inhabitants could see in the dark; but were near-blind in sunlight (the not-Space Marines at least).

That's about the only way it 'could' work for long, and it may as well be a Homeworld Trait or something and not a mutation.

Plushy said:

There is no way Big Eyes would scape notice, since lacking eyelids is quite a noticeable thing. Though skin would pass casual inspection, but not any kind of medical check-up. Feel No Pain and Wyrdling are indeed hideable, though hiding Wyrdling not so much as you'd be an unsanctioned psyker and therefore highly volatile. Regardless, those are 2 results out of a 10 element table, which among the two of them give only a 20% chance of not getting executed every time you earn a mutation. If you're lucky enough to survive the first, the second only has a 10% of survival. And even if you're the luckiest abomination on the galaxy, the third mutation would be instant blamming, no save.

Hardly desirable chances.

 I think others would agree that it's more trouble than it's worth to use the DH tables for OW. I'd rather have guardsmen die on the altar of battle than because they have developed scaly skin or something like that. But while it might not be a good fit for the main rulebook you can of course substitue it yourself for your own home games and have a higher concentration of warp energy in your game.