[Spell] possession spell for transport ships

[ferdanand]

making a pirate themed map and having an issue regarding 'boarding' abilities.
I have used possession via a summoned unit "boarding party" that is able to without issues take control of an enemy combatant ship, but i am unable to do this against ships that are transports, a serious issue as ideally all boats will be able to transport units around the islands.
Is there a way to bypass this so that it takes control of the transport or do i need to just move onto another idea with a different model?

 

[Tickles]

Units with Cargo Hold can't be possessed, but you can add Cargo Hold through a trigger.

Edit: I'll just attach an example map. It uses Chain Lightning as a dummy ability to remove Cargo Hold. A dummy unit automatically casts possession right after, and then Cargo Hold is added back to the ship again.