I don't have any or am not able to make any GFX, so gfxers, feel free to take this as a challenge if you want to.
I was thinking of a long rifle or a machine pistol, or a machine pistol that could look like machine pistol with a long barrel.
The main feature on this gun would be it's two different modes. In it's automatic mode, I'd imagine its firing speed to be around the dame as the Tec 9 or a little faster. In it's 3 burst mode I'd image three bullets at once, tightly close behind each other. Of course, this type of capability would require a slower firing rate, which I could describe as a slightly slower shipka.
The body of the gun could be sleek like the shipka itself, except with the long barrel. Again, it could be a machine pistol or a long rifle. As long as it looks semi futuristic like the lexel.
Anyway, if you choose to take this as a GFX challenge, post your visions here!