If you are a Nomad researcher or Order pilot, no problem, [Core]-members should be allowed as well, Zoners are fine too I think, and Corsairs exchange technology with the Order regularly, so a few of them may have nomad weapons as well, but all other players shouldn't really use them without having a REALLY good RP reason for it.
As for humans picking up Wild weapons: I think a good RP reason to restrict their usage would be just saying that to mount those weapons on standard weapon ports the ship would need to be modified heavily; most people shouldn't be able to do those modifications themselves, no lawful engineer would do it and most unlawful engineers wouldn't do it either, fearing Nomad infection etc.
Edit: Ew, sorry for participating in the gravedig, haven't been looking on the dates of the posts except for the last one.