*cough* I think he said xbox360, you can get mods for them, but usually not weapon mods
What? If you put any weapon mod on the Weathered 10MM Pistol it results in a giant square with an exclamation point on it because that version of the 10MM was never skinned to have mod on it. Only way to fix this is to reload a save from before you attached the mod to it.
They forgot to put in the meshes of the modded 10mm, you're seeing the no mesh warning. Just remove the classic pack, make a save and add it back. Don't put mods on it again.
The weapon mods in the vanilla game for the 10mm pistol can be installed on the Weathered 10mm Pistol from the pre-order pack. Problem is that weapon shouldn't have been a valid weapon to mod and it's missing the data to show the new moded pistol. The red triangle with an exclamation mark is a visual error message. Go, go QA department!