That sounds like a good idea.
If I may suggest - I think crossbows would work even better for them. They got the "gun" hold, look "grim dark" enough, and you can glue on some techno gimmicks, bitz and whatnot to make them look all Predator style (Kukukukukukku... you now the sound he made
Plus - if you take a look at the Mounted Knarloc with that balista on his back - despite the permittivity of the weapon the design itself seems kinda.... "normal" for the Kroot. Thats where I am coming from