Suppose that Jonah is on the same ship as Papa Doc. Would Jonah’s ability force any possessed crew to take up cargo space, or would the possessed crew not take up cargo space, per the Code entry?
That line in the PC entry for Papa Doc should be applied as a rule, which means it can be overridden by other abilities, but even if it was part of his printed ability text, Jonah’s “always” would still take priority, so the possessed crew will take up one space each.
As an extension of that, if you have Jonah and Papa Doc on the same ship, but no free cargo spaces, you won’t be able to use Papa Doc’s ability at all. You can’t “possess” a crewmember just to immediately toss them (or anyone else) overboard.