I understand it need a lot of hassle for be feasible, the underhivers are the most low tier of "humans" in this dimension. I read somewhere if you wan create a "quick" shooter like weapon, it should need more speed (correct me if I am wrong).
Actually the Necromunda part of the universe, I donīt know that much, cause I was glued to PCgames of WH40k, a reading from miniaturegame codex for those armies plus the basic manual.
Having some in mind like a pretty tunned down little ambush groups, than comes in this mod.
My ideas are:
Necrons: We all know how powerful are this race, but a underpower unit for them are logical in some points, like a dysfunction in the regenerative metal they have, malfunction-crumbled crypt. We all know about those possibilities than comes in the supplements. You canīt loot then easily because the vanishing technology they have for avoid reverse engineering their weapons. Even with a underpower moding, they can be a late game foe.
Imperial Guards: At the start I was seeing then like small force than could be summoned by a expensive way, maybe resources or maybe because you settlement please a lot the Emperor, and depends how much you are pleasing the Empire, you get better chances they help you in some raids. About Las-Weapons, talk with Mep or Putnam about if they are posible (if you donīt do it already), and depends how they looks in the practice, you can tunned it up or down or remove it. (experimentation)
Edit: Las-weapons not all the time should be like the elite ones than are in the core of Imperial Army, thy could be a less quality one, salvaged, looted from an old-old battle in that zone.
Eldars: A bit like Necron suggestion, in this case we all know they tend to appear sometimes in small groups to raid Necrons or just as scouts. Again other posible late game enemies if this mod goes more far. For sure we will have a better weaponry to fight in some equality way.
You can try ask to Putnam, or Mep probably other of many good modders that are here if some stuff are possible via, DF hack.
Sorry if I sound like is "easy" and I know is not, also, is your time. Just I want to see a mod in this kin of universe than could be big as MWDF.
EDIT: The DFhack included inside this mod, is compatible with the falconneīs plug in pack?