I'm torn on the Ogryn idea. Part of me would love to play an Ogryn, but another part of me is certainly hesitant due mostly to how GW has far more often than not portrayed them as stupid to the point of being nearly handicapped and the comedy relief.
My biggest issue with Abhumans is they aren't typically in mixed units. they are kept quite separate. Maybe an Ogryn bodyguard here and there. But you don't see a random Ratline sniper in with any given Guard regiment. Let alone Ogryns. They're their own thing.
I could see a Abhuman in a mix regiment. as individual squads or even companies. like a Ogryn squad attached to a armour patrol or a ratling sniper with a scout squad. more as a loan than an accutal part of the regiment. to take a leaf out of the US military, we have some airforce personal attached to and agmenting army units.