These are ideas i have had over time, and, in my opion, might be interesting additions in the future...
1) Crafting, of sorts. I think it might be interesting, to be able to convert those 6 rusty BB guns, into a single hardened model. Well, more precisely... two rusty ones for a regular one, two regular ones for an enhanced model, etc. - up to rare level models, but not legendary versions. This could be a part of a new room type addition - or part of the existing armory room. Maybe the crafting takes time, etc. Overall, i am unsure how to mod it since i am not a game designer.
2) Some additional "collectables"... some benign like say, a Garden Gnome, etc. And definetely - BOBBLEHEADS. The Bobbleheads could be limited to the SPECIAL stats that, perhaps, enhance training time a little bit... maybe only one per stat... be a Legendary type item to eb found in the Wastes and/or Lunchboxes...
That's all i remember right now... thoughts?