Its taken awhile to get a large amount of mods so far (prob still missing alot) but already have found that guns are tied to specific elements. Like pulse rifles are always arc mods, hand cannons void, fusions solar, auto rifles are solar as well. You can use some universal mods as well for some guns. Sort of make me look at what they thought were synergistic weapons that they put together on elements and try out those combos. Does it stop me from using other guns if I can't put their mods into my armor? No it does not. Has it taken me a bit for it all to click into place and start understanding whats going on with the new system, it has, and its clearing up the more mods I get and I got alot already from turning in my meager amount of weapon parts to banshee (only about 5K worth). Gotta give it more times than less than a week to understand it and see how it functions before making an informed decision on it.