My overall idea:
It should reload long time and only with few ammo (like 4 grenades per reload), also launched grenades should explode in lower range but you would be able to launch 4 in short time. Below is my early model without textures and simple pencil-drawn "concept arts".
Now this model has 868 faces but I'll remake it.
Colors of a weapon will be futuristic:
something like image below (or black and orange/red) - no matter which colors will be used - line (seen on concept sketches) will be glowing in the dark
What do you think about grenade launcher in Red Eclipse? Would it be something good or bad?