I've looked at the Inquisitor Navigator rules, and at Rogue Trader's rules, but can't find an answer in either direction - are Navigators able to use Force Weapons? Also, would they be subject to other psyker-specific devices, like Warp Disruptors and Psyk-out rounds?
Into the Storm, P127: "Although Navigators are considered psykers, their powers are different from a regular psyker and they do not gain any of the benefits for using a force weapon".
I'd say that's as fair an answer as you'll get.
Hmmm, had missed that part... Ah well. Any suggestions for an interesting staff/spear type weapon then?
Shock staff! Same as a shock maul, but Reach: 4 and you don't add on any bonuses for Strength unless you're using it two-handed. My Savant-Warrant has one.