I don't have them, but the arms should be interchangeable between
AOBR, Deathwing, Normal and Assault terminators. If anything, you will have to remove the pin from the body side of the shoulder on the
AOBR minis to get a clean join to use other arms, but that's it.
Legs won't be interchangeable, because the back of the torso and the legs of the
AOBR termis are molded as one piece. Also the helmet is part of the front of the torso, not separate.
I am looking at the picture of the sprue from the Warstore, and unless the Ultramarines icons are
very small, I don't see a thing. They look like the normal plastic Terminators, just mono-pose.
I notice there are 5 spare shoulder pads on the Deathwing Command sprue, so that's a good start to making them look Deathwingy.
The shoulders are molded onto the arms unlike the multi-part minis so the pads won't fit, but the right ones are perfectly clear to add decals to.
Especially if you are using the Knight robed torsos with the main Deathwing box legs, I don't think you will have any problem with adding the additional bitz to the
AOBR terminators, other than possibly, the Deathwing torso fronts might not match up. But all the wargear and arms should.
I actually think you might want to try using the Dark Vengeance terminators instead, as they only run about $15 from places like the Warstore.
You would have to cut off the molded-on left arms arms, though, if you want to add things like the left lightning claw or the storm shield arm. But.... if you just want to add right arms and possibly the missile launcher on one of the torsos, they would be a
much cheaper alternative to the
AOBR minis, and they already have the
DW iconography molded on.