So it should be well known by now that boxes sometimes contain unique weapons. These weapons are a lot like the RTC items in that they have a special effect unique to themselves and can't be modded. Personally the only really unique thing I see about some of them are things like a built in scope and exclusive firing modes like burst fire. I'm against making these unique items skins for their parent base. Doing that would reduce the overall variety of weapons and do nothing more than add yet another skin to the same weapon.

I propose instead that the unique weapons such as the Iron Bane or the Mercury bolt pistol for example have either locked mod slots for certain slots they already have mods in (as many have asked for before such as sternguard bolters having no scope or magazine slots due to the scope and drum mag already included) yet can be modded in slots that are already empty. This OR that they have mods unique to them, mods that only fit on said Iron Bane or Mercury bolt pistol and not their parent weapons.

Now that I think about it I'd actually like a hybrid system of this more. Unique weapons come with unique mods and open slots. For example, the Sternguard bolter could come with a drum magazine and a scope. Those two slots require mods unique to the Sterguard to be replaced while the grip and Muzzle areas could use mods that fit any regular bolter.

Pretty sure I saw an Elder unique that did 2k damage lol also there is a crozius that does fire damage that just pwns absolutely everything. I think the people using them would be pissed if you took their uber toys away.

Also coming to think of it isn't there an unique Ork gun that deals poison damage? Nurgle says give CSM one now also if there is. .. and even there's not.