If one were to think about integrating some of the weapons/armors from the DLCs into the worldspace, it would have to be somewhat methodical, and take a few opinions to each on how, why, where, when (and other similiar questions perhaps?) for each item to be there.
Like take for example the .45 pistol. What reasons do we have for it being in the Capital Wasteland, how would that be integrated, why, where would it be placed, and when might we see it? I would say that if it were to be placed in DC, it would be there to diversify the weapon variety in the world, to give another optional caliber, and to provide some consistency for the world. What reason would there not be for the .45 to not be there?
Other questions I assume would likely ensue, but then comes the question of why it shouldn't be. Now one reason might be that it should be a thing consistent with the area it was experienced in, that it was meant to be for that area, and maybe other things come into play. Maybe its a question of balance, maybe its a thing that some DLC guns don't belong there for other reasons, things like maybe the LAER, the Sonic Emitter, the Red Glare.
Don't know whether to consider it in the scope of TTW to have it, but it sure as hell could make an interesting companion mod to integrate some or more of the common weaponry from each game into the other on the DLC side instead of just the vanilla weapons.