It's not odd as they're dressed up to look futuristic. You wouldn't know that was a Thompson under the PR without being told.
But as I said before, there's nothing wrong with adding rails to it. It's unfair to call it "COD" fanboy wankerisms or whatever as it is what modern rifles are doing. It is realistic and it is happening in the real world and it's not due to Call of Duty (and I hate that game too). And again, as I said before, there's a level of restraint to be had and for me that is the unnecessaryness (yes, I know it's not a word) that is the PEQ box.
There's nothing saying this isn't following the Aliens aesthetic. We've seen one prop so far that is undeniably a Pulse Rifle with added realistic flavour. I'm hoping this isn't the final look for the thing as I'm not fond of some of what's on the picture but to condemn the film based on a little tease is unfair.