In the day and age of 40K, I can see extra organs put in standard humans. They are given chem mixes that make them go into a rage (like an Eversor assassin). Look at the Mechanicus. They augment their body to become more machine like. They don't start out as all advanced, but gradually work their way up. I can't say that I've read any where that extra organs were implanted, but I can't see why the technology is not there.
As for that guys IG army, if it's his fluff for his own army, I'm perfectly fine with that. However, if he is doing it and boosting the stats of his IG troopers, then that's a huge no go. So fluff wise, yes. Game effecting wise, no.
Edit: I would love to see a hockey themed army. Especially a Detroit Redwings one!