Yes, i think there could be an option to follow:
* Laser Pistol + Plasma Pistol + Clip => Some new hybrid pistol technology. It could provide more speed and damage than both.
* Laser Rifle + Plasma Rifle + Clip => Some new hybrid rifle technology. It could have seriously upgraded aiming mode that would actually be useful, allowing perfect CTH even for people with lesser accuracy (say 150% or 175% built-in accuracy). It could have less accurate than plasma rifle, but faster to compensate (and overall better) snap shots. And have more shots per clip
* Heavy Laser + Heavy Plasma + Clip => Some new hybrid heavy weapon technology. It could have unlimited ammo (since in a bigger gun its easier to fit a compact reactor that makes it powered forever or require recharege only after combat) or built-in 100 or so shots. Maybe it could be even directly elerium-fed (meaning, it costs 1 elerium to recharge, say, 50 shots at base). It could have damage surpassing heavy plasma so it would blast ufo walls easier. Would also be faster (and have a reasonable aimed shot mode, again, as both rifle and heavy plasma have useless aimed shot modes)
* Blaster Launcher + Bomb + Small Launcher + Bomb => Some new hybrid autocanon-like technology. Having multiple ammunition possible, it could load stun, he or plasma projectiles. It would be heavier than autocanon, but pack a seriously bigger punch, close to that of a rocket launcher lg. With autofire capabilities
* Alien grenade + Psi tech => Some new psi-grenade that would deal new damage type that only harms living beings, ignores items and walls. It would also probably go through them completely. Target would use its Psi resistance instead of armor to protect itself from this kind of damage. Should be very fun means of cleaning those aliens behind the door.
Problem is - does X-Com needs a better weapon tech?
Maybe X-Com needs to have some handicap when using alien equipment - like, -15% chance to hit since its unusual to humans (not made for their kind of hands etc.) Since otherwise, due to aliens providing generous supply of heavy plasma, and heavy plasma being like second best to-go weapon in the game (considering damage,speed,and accuracy) (after plasma rifle, imho, which just owns with it 85% snaps) (but having benefit of more damage and being able to breach ufo walls which can argueably help alot).... well, there is no need for better weapons.
In fact, this game lacks better armor, not better weapons. (And bigger item limit!)
With heavy plasma (provided you'd not have problems with item limit) every person in your squad can down every single alien in the game (maybe except sectopod) in one-two hits, reliably, with serious accuracy.
What else do you need?
However, in best flying armor, you can still very easilly go dead one-shot from two most common enemy endgame weapons in the game - blaster launcher and heavy plasma.
Maybe an advanced armor is what we need? Something providing more armor than a flying suit, but without flying capability and having more energy spent. Something that turns your soldiers into a walking mecha. But at a cost of course - of lesser mobility. That would also make you choose between mobility and defense - which would make serious sense, since right now your only limit is resources.
PS: As a side mod, something could be done that would make X-Com seriously handicapped when using alien equipment or outright not being able to use it, at all.
This would require an alternative research route (after laser and plasma are through) that would create new technology that would rival those of aliens (then it could even have similar stats, just different looks and sounds). Like "here's our Human response to your Alien heavy plasma!"
Same for grenades and every alien stuff. Would make sense, really.
