@Ascadix: Thanks for the ruleset. I think I have the graphics for the improved shotgun somewhere. The reason I did not include it in the XAE along with the regular shotgun is that I find it weird to have an improved version of shotguns but not of any of the other conventional weapons. If we make better shotguns, surely there should be better rifles, better autocannons, better...
It also begs the question: Do we really need an extra tier of weaponry beyond conventional -> alloy ammo -> laser/gauss -> elerium laser/depleted elerium gauss -> plasma. I am all for delaying tech, but as of now I find little space to add a new tier of alloy guns with alloy ammo.
That's also why I don't have explosive elerium based conventional ammo. I have, however, completed a new expansion module for elerium explosives since explosives did not have multiple tiers and I pretty much designed it already because of the discussion with Hobbes in another thread.
All that being said, I will incorporate your work into an expansion module, since I believe in the mod offering options. If you do further work on this idea, let me know! Despite my reserves, I am very much interested. The later XCom gets laser/gauss/plasma, the happier I am. (I prefer slower tech gains as they are more realistic).
======== Regarding plasma weapons splitting =======
There are lots of possible ways to explain alien weapons being useable only by aliens, DNA based locks and psi-links being the two best candidates.
You can even extend the psi-link one into triggering a self-sabotaging mechanism when its user loses consciousness. You still retrieve a pretty looking alien gun that's worth money but it doesn't go pew-pew anymore. Then XCom engineer take whatever parts still works, rig something together to make the gun shoot again and you end up with a subpar version of the weapon. That, and XCom troopers don't like guns that shoot when you think "pew-pew", they prefer triggers which are an incredibly primitive idea for the aliens. I think that sounds pretty good.
Anyhow, the handwaving is far from my main concern with this idea (which is not gonna happen soon any ways). I am considering it for the technical side of being able to rebalance endgame weapons for both aliens and XCom. It particularly annoys me that as soon as XCom has heavy plasmas, everyone carries one, whereas the aliens are still stupid enough to carry pistols and rifles, especially with the Alien Armoury Expanded. Not that I consider that a flaw of the AAE, I very much like it for that reason, in fact. We just need the same to be true for XCom.
Edit: And because I kept thinking about this:
Yeah, because alien weapons require opposable thumbs, which humans clearly don't have. 
Doesn't it just require a trigger finger? That's even less special! I want to give a heavy plasma to some raccoon now!
Like this guy, he already looks like he could be an XCom operative! Just need to recolor the orange to grey and the armour to a suitably purplish blue for alien alloys.
All joking aside, I'd love to move on from the "what plasma for humans and how?" questions
This is some ways away.
