I agree with the suggestion of pistols for the javelin rules, due to the 10" range. More specifically, pistol and hand weapon, since the javelin counts as a hand weapon in melee. Handguns should probably count as crossbows, due to slower reload time, and crossbows should count as bows.
Honestly, the javelin is kind of a strange weapon to include, since it will probably fit fewer warband themes than if we had, say, a 12" ranged weapon that could represent pistols, throwing weapons, and even shortbows, etc.