At the minimum, this gives more value to merchant missions. As of right now there's virtually no incentive to steal animals or cages.
Taking the voyage would give your crew the maps while the robbed pirates would no longer see them. If they remembered where to go, though, they should still be able to get the chests/skulls/etc. before the thieves do (and/or steal the maps back).
Perhaps the pirate who stole the maps drops a message in a bottle containing the voyage if he/she dies.
