Yep, a lot of battlesuits, the elemental included, have modular weapon mounts.
Fluff wise, modular weapon mounts were inspired by omni-pod technology. Basically a mounting hardpoint and standard connections for power and fire control.
You can easily swap the weapon in the modular mount out for another one; that's the whole point.
If it lists a modular weapon mount, you can swap at will, if it lists a weapon, it's fixed equipment.